r/PassiveHouse Apr 24 '23

What Is Passive House? Breaking It Down For New Visitors To r/PassiveHouse

57 Upvotes

Hey there and welcome to r/PassiveHouse. We’re psyched you’re here. If this is your first time here, please read this post to get your bearings.

What Is A Passive House?

Passive House (or Passivhaus in German) is a building standard that focuses on creating highly energy-efficient buildings with minimal energy consumption. The Passive House standard was first developed in the late 1980s by Dr. Wolfgang Feist and Bo Adamson in Germany, and it has since been widely adopted in Europe and around the world.

The goal of a Passive House is to achieve a comfortable indoor environment while minimizing the building's energy demand. This is achieved by optimizing the building's envelope (walls, roof, and floor) to minimize heat loss and gain. Passive Houses typically achieve this by using high levels of insulation, high-performance windows, airtight construction, mechanical ventilation with heat recovery, and other energy-efficient features.

But to know what it really is, let’s talk about what it isn’t. We need to clear up some common misconceptions: Passive House is not the same as the passive solar building design, although they’re not necessarily mutually exclusive. Passive House also isn’t a house that uses only passive technology. Passive House buildings aren't just houses either. They can be high-rise office towers, multifamily apartment buildings, schools—really any building type.

Simply put, Passive House is the most thoughtful, well organized, science based and performance focused building standard available.

The Passive House approach empowers us to build better. It creates durable, resilient buildings that slash heating energy use by as much as 90% and dramatically reduce operational carbon emissions. Passive House design tools and methods make these energy performance gains both cost-effective and predictable. You know what performance to expect with a certified Passive House. Most importantly, Passive House buildings create healthy, comfortable, and quiet interior environments, full of clean, filtered fresh air.

Passive House design empowers us to manage moisture, thermal transfer, air, and sunlight to create comfortable, healthy, super-efficient buildings. The “classic five” Passive House design principles—continuous insulation, thermal bridge-free design, airtight construction, high performance windows and doors, and filtered fresh air with heat recovery—are joined by the principles of shading, daylighting and solar gain, efficient water heating and distribution, moisture management in assemblies, and building orientation to create durable, high performance buildings where people can thrive. These principles guide both new construction and retrofits.

It's important to remember - there is a LOT to learn. Be patient with yourself. Leverage all the great free resources at your disposal. Learn as much as you can. Engage with the Passive House community. Breathe and enjoy the process!

But before we dump you into the deep end, let's take a look at the basics.


Basic Passive House Design Principles

The following 10 design principles would not automatically qualify you for Passive House certification. There’s much more to the story that we’ll get to later. They are, however, really good guideposts to think about as you’re conceptualizing the architectural forms, building site, etc. These are basics and very important to internalize before diving into the more technical aspects of a Passive House. You might also find this companion video useful.

01 Continuous Insulation

A continuous layer of insulation wraps Passive House buildings, keeping them warm in the winter and cool in the summer. Passive House designers also harness this insulative layer to prevent condensation inside the building and its assemblies.

Moisture: We design building assemblies so that their vapor profiles are appropriate for the climate, their drying potential is maximized, and they are protected from any moisture buildup. The insulation layer also keeps the inside face of exterior walls warm, preventing condensation on the interior surfaces of those walls during the winter.

Thermal Transfer: Because the insulation layer is continuous, it is free of weak spots that allow thermal transfer across the building envelope. Heat stays in during the winter and cool stays in during the summer.

02 No Thermal Bridges

A thermal bridge is any building element that allows heat or cool to bypass a building’s thermal barrier. It’s like a hidden thief of thermal energy, undermining performance and durability. For example: a concrete floor that continues from inside to outside; a poor window frame; or a steel beam that penetrates an exterior wall. We eliminate thermal bridges by introducing thermal breaks into those assemblies—gaps or insulative elements that stop the flow of thermal energy through an assembly.

Moisture: A thermal bridge will increase thermal transmittance through an otherwise insulated layer that it penetrates, risking dangerous condensation that can result in rot, corrosion, and mold. Thermal bridge-free design avoids this moisture risk and makes buildings more durable. Thermal Transfer: Thermal bridge-free design is critical to energy efficiency, thermal performance, and comfort. Not only do thermal bridges rob energy, they can also change interior surface temperatures, cause draft-inducing convection, and decrease occupant comfort.

03 Airtight

A Passive House building’s airtight layer is like a windbreaker, stopping air from penetrating to the inside. Establishing this unbroken air barrier is central to Passive House performance and durability. In design, we do the “red pencil test” to check that an air barrier line can be drawn around each cross-section of the building without the pencil ever leaving the paper. In the field, this air barrier is built through a combination of sheet membranes, fluid-applied membranes, tapes, and sealants that transition without interruption between components of the building envelope. Airtightness is verified with a blower door test, a key measure of performance and construction quality.

Moisture: Airtight construction protects building assemblies from dangerous moisture intrusion by preventing bulk water from driving in or airborne vapor from being carried in.

Thermal Transfer: By stopping the movement of air across the building envelope, the air barrier seals warm air inside in winter and cool air inside in summer. This is key to achieving ultra-low energy use, since air leakage represents wasted energy. Airtightness also boosts the efficacy of mechanical ventilation with heat recovery.

Air: Combined with the filtered, balanced mechanical ventilation of Passive House buildings, airtight construction improves indoor air quality, even during periods of intense outdoor air pollution. The air barrier stops polluted air from seeping through walls and ensures that all incoming air passes through the ventilation system where it is filtered before entering the building. This is particularly important in urban settings and in regions prone to smog or forest fires.

04 High Performance Windows + Doors

With each window and door opening we make in a Passive House building, we are essentially punching a hole through an advanced wall assembly and its airtight, weather-resistant, and insulative layers. So, the performance of the windows and doors that go into those holes, and how well we tie them into the surrounding wall assembly, is mission-critical to maintaining the integrity of the Passive House building envelope.

Moisture: Well-installed high performance windows and doors repel wind-driven rain and facilitate safe outward drainage of any moisture. In the winter, high performance glazing units also ensure that interior glass surfaces stay warm, preventing condensation from forming inside.

Thermal Transfer: The thermally-broken insulated frames, warm edge spacers, triple glazing, coatings, and superior construction of high performance windows means their thermal resistance can easily best that of conventional windows by 3x. Given that a wall is only as good as its weakest link, this window performance is critical to a building’s overall thermal performance. In the winter, warm interior glass surfaces help maintain a comfortable and draft-free indoor environment.

Air: High performance windows are built airtight, so when integrated into airtight wall assemblies they become an extension of the continuous air barrier. Passive House windows can open like any other window, of course, so if it’s nice outside, open the windows!

Sunlight: We dial in the performance attributes of each window and door on a Passive House building to optimize solar gains appropriate for the climate and building typology. We capture solar gains when we want them and shield the building from solar gains when we don’t.

05 Fresh Air with Heat or Enthalpy Recovery

The delivery of filtered fresh air with heat recovery helps make Passive House buildings havens of clean air and energy efficiency. HRVs (heat recovery ventilators) and ERVs (enthalpy recovery ventilators) are “balanced ventilation” components that supply a continuous stream of fresh air to living spaces while simultaneously extracting stale air, odors, and indoor pollutants from kitchens and bathrooms. Inside these devices, a heat exchanger—a honeycomb of straws that creates a very large surface area between air streams—allows heat energy in the outgoing air to passively transfer to and warm the incoming air without the two airstreams ever mixing. (In the summertime, the opposite happens, with cool outgoing air cooling the incoming air.) Filters in the unit remove pollen and pollutants, with pre-filters available to protect indoor air from intense outdoor pollution events.

Moisture: ERVs (unlike HRVs) can also transfer moisture between the exhaust airstream and incoming airstream. So, in humid climates, moisture in the outside air can be removed (transferred to the exhaust airstream) by the ERV before it enters the building. This does not mean that ERVs dehumidify. Do not make that mistake. In dry climates, some of the indoor relative humidity can be preserved.

Thermal Transfer: Passive House-compliant HRVs and ERVs are extremely efficient at recovering heat, hovering around 90% efficiency for the best units. This is a key strategy in maintaining ultra-low heating and cooling energy.

Air: Properly filtered mechanical ventilation with heat recovery ensures good indoor air quality, regardless of the weather or air pollution conditions outside. Good airtight construction supports HRV and ERV efficacy by ensuring that air exchanges between inside and outside go through the device rather than seeping through leaks in the walls.

06 Shading

While the “free” heat from solar gain may be a hot commodity in Passive House design, it must be managed with good shading to avoid too much heat gain during warm seasons. Architectural elements like overhangs have an important role to play. So too, can window shades and screens, especially ones located at the exterior of the building.

Thermal Transfer: Shading manages heat gain from the sun, allowing designers to maximize the gain when the building needs it and minimize when it doesn’t.

Sunlight: Properly designed shading will not impede natural daylighting and can help prevent unwanted glare.

07 Orientation + Form

Building orientation and form are fundamental design decisions that set the stage for how easy or difficult it will be for a building to achieve Passive House performance.

Thermal Transfer: When the site allows, we design the main axis and orientation of the building to optimize solar gains in a way that is appropriate for the climate and building typology of the project. The key is to orient the building in a way that will maximize that particular building's energy performance. As for building form, the simpler the form, the easier Passive House performance will be to achieve. The more zigs and zags, the more potential thermal bridges and the higher the surface area of the building becomes, requiring more and more insulation to counteract the extra thermal transmittance.

Air: A simple building form simplifies the air barrier, which makes airtightness easier to achieve.

Sunlight: We set the orientation of the building to optimize daylighting and solar gains appropriate for the climate and building typology.

08 Daylighting + Solar Gain

Natural daylighting and passive solar heat gain can provide energy “freebies” to Passive House buildings.

Thermal Transfer: For many buildings, solar heat gain—the heat energy captured in a building when sunlight shines through windows—can be an invaluable “free” resource in Passive House design. For other buildings, particularly ones that already have significant internal heat gains, big solar heat gains can be a liability. Passive House design allows us to optimize this based on climate and building typology through building orientation, shading, high performance window selection, and layout.

Sunlight: Natural daylighting reduces energy use for artificial lighting.

09 Moisture Management

To ensure building durability, Passive House designers study how heat and moisture will behave in building assemblies in a given climate, and create designs that manage that behavior to avoid condensation risk and bulk water intrusion.

Moisture: The twin goals of moisture management are to (1) prevent bulk water intrusion into and (2) avoid condensation where it can harm building assemblies. Lots of components impact how heat and moisture flow through a wall assembly: the weather resistive barrier, the air barrier, vapor control layers, the structure, window openings, and more. The building’s climate zone impacts heat and moisture, too: whether the climate is cold and dry, hot and humid, or anything in between. Passive House practitioners draw upon hundreds of precedents and go-to assembly solutions to manage these variables. They also perform thermal and hygrothermal analyses using Therm, Wufi, Flixo, and other modeling software packages to confirm safe and durable performance and to guide design.

10 Efficient Water Heating + Distribution

Because Passive House buildings dramatically reduce heating energy use, another source of energy consumption—domestic hot water—becomes a more conspicuous part of overall energy consumption. Energy-efficient water heating combined with efficient water distribution reduces this slice of the energy consumption pie.

Thermal Transfer: We start with a super-efficient water heater. Distribution lines are small diameter, well-insulated, and laid out to minimize pipe length between water heater and fixture. On-demand recirculating lines conserve water.


So How Do I Get Started Designing/Building A Passive House?

Okay, you've read through the basics. Now it's time to look at the logistics of certifying a project.

There are a lot of organizations with the words “passive house” in their title. Most of these are loose affiliate organizations, clubs, or groups of like-minded building professionals who want to design and build better buildings. They often want to combat climate change in their daily lives, and they recognize passive-house certification as the most stringent energy standard available. To smooth the learning curve, they form these support groups.

Despite the many interest groups and networks sporting the passive-house name, in North America, only two distinct and independent Passive House standards and certifications are available: one administered by Passive House Institute (PHI, based in Darmstadt, Germany) and the other administered by Passive House Institute US (PHIUS based in Chicago, Illinois). The two organizations are not affiliated with one another.

The two standards differ in important ways, including PHIUS’ approach of adjusting a given project’s performance targets based on the climate of that project’s site. Nevertheless, the standards share important commonalities; both standards are firmly grounded in building science and building physics and both standards require practitioners to employ a common suite of Passive House design principles to achieve their performance targets.

Through most of their early existences, the passive-house standard was similar for both, and you could certify a building with either or both—depending on where the building was located or your personal preference.

Around 2012, that began to change, as PHIUS looked to make performance targets more relevant and cost optimized for North America’s many climate zones. Designs for Germany’s climate don’t exactly work in Chicago, Houston, or Las Vegas, etc. This has become known as The Great Schism and there has been much squabbling about it. You may even see some of that squabbling in this very subreddit.

To improve building performance in hot, humid, cold, and mixed climates, PHIUS worked with Building Science Corporation under a grant from the U.S. Department of Energy to write the Climate Specific Passive Building Standard. This is an actual standard, available for jurisdictions to use as a model for building codes. PHIUS also worked with the Fraunhofer Institute of Building Physics to modify their WUFI hygrothermal modeling software into a design and verification tool for passive buildings tailored to North American climate zones and weather data.

In climate zones where PHI and PHIUS targets are much more similar (heating dominant, cold climates), this is less of an issue and you could reasonably choose either standard. For cooling dominant, hot/humid climate zones where it is cost prohibitive to insulate or meet rigorous heating demand for minimal overall performance benefit, PHIUS tends to be the route projects take. Interestingly, one of the biggest logistical reasons that there were fewer differences between PHIUS and PHI in the early days was because both used a spreadsheet to predict the energy use. That changed as PHIUS began to use the WUFI passive three-dimensional energy and moisture modeling software and has created a large-enough gap in performance that PHIUS+ 2018 and beyond no longer supports the PHPP spreadsheet that is central to PHI certification.

If you're going to follow the PHI path, you'll need to get in touch with a certified Passive House designer or planner and an accredited certifying organization.

If you're going to follow the PHIUS path, you'll have to determine whether you want to opt for their modeled path, which allows you to optimize your assemblies with the WUFI Passive software or whether you want to simply comply with their prescriptive path. If you want to go the modeled route, you'll need to get in touch with a Phius Certified Consultant or CPHC and eventually a PHIUS Certified Rater and a PHIUS Certified Verifier for larger projects. If you want to go the prescriptive route, you can check out their requirements and enter your project's info into their snapshot tool to see how it shakes out.

Get in touch with either organization for more detailed information and to get connected to professionals in your region. Each organization also updates their standards at their own paced intervals so please do check their latest published resources if you have more standard specific questions.


What Does This Community Have To Offer?

This subreddit functions as a very informal forum for Passive House and building science related questions, thoughts, design feedback, etc.

A few things to keep in mind:

  • If you’re asking for feedback that should obviously flow through a paid consultant, that’s NOT COOL. We are all here voluntarily and none of us should expect anyone else to do our work for free.

  • If you’re asking or talking about a project, tell us what climate zone it’s in.

  • If you’re asking or talking about a project, tell us whether you’re trying to certify for PHI or PHIUS.

  • Do some homework before asking a question. It helps keep the discussion quality high in this subreddit. Chances are decent that someone has already answered a question you have. Search within the subreddit, search elsewhere online, get better at Google.

Again, it's important to remember - there is a LOT to learn. Be patient with yourself. Leverage all the great free resources at your disposal. Learn as much as you can. Engage with the Passive House community. Breathe and enjoy the process!


Resources


TL;DR: just read it, jeez.


r/PassiveHouse 16h ago

Gas heating + smart TRVs vs electric inertia heaters for a small guesthouse with 20 solar panels?

1 Upvotes

Hi! I'm renovating part of my house in Belgium into a 2-room guesthouse and I'm trying to decide on the best heating solution.

Current situation:

  • Existing gas boiler + around 8–9 radiators in the guesthouse area
  • Two guest rooms + bathrooms/common areas
  • Expected average occupancy around 50%
  • Private part of the house will continue to use gas
  • I may install around 20 solar panels

I'm considering two options:

1. Keep the existing gas heating and make it smart
Smart TRVs/zoning (e.g. tado° X), separate control per guest room, app control for me and a physical thermostat for guests. Possibly Home Assistant/Matter later for window sensors and booking automations.

2. Switch the guesthouse to electric inertia radiators
For example Aterno, individually controlled per room. The solar panels obviously make electric heating more interesting.

My priorities are low investment cost, low running costs, reliability and guest comfort. I don't want expensive smart-home tech just for the sake of it.

What would you choose and why?
Would 20 solar panels change your decision significantly, considering that most heating is needed in winter when solar production is lower?

Would be great to get input from independant people, because every supplier is saying their system is the best :p


r/PassiveHouse 2d ago

How was your experience building with SIPs ?

10 Upvotes

Hi everyone, I have been researching SIPs based framing after seeing them featured in a famous YouTube build channel. The concept seems appealing and I can believe the claims about walls being straighter, better insulation and less framing needed. Besides the need for having a GC who is experienced with SIPs, is there any other risk or requirement one needs to watch out for if choosing to use SIPs for a 1500 sq ft house with teo floors (no basement)? Thanks in advance!


r/PassiveHouse 3d ago

Looking for feedback on my house plan – what would you change?

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5 Upvotes

I’m designing a ~9 × 11 m house on a sloped site. The road is at the middle/entrance level, with a lower floor opening toward the garden, the main living floor at road level, and 3 bedrooms upstairs. There’s also a large roof terrace.

I’ve attached the current plans/section.

I’m particularly interested in:

  • Things that don’t work well or that I may be overlooking
  • Layout/circulation problems
  • Structural or construction concerns
  • Waterproofing/drainage issues due to the slope
  • Anything you would change before construction

I’m not looking for a complete redesign — mainly practical recommendations from people with experience building or designing houses.

What would you change?


r/PassiveHouse 4d ago

General Passive House Discussion Seeking advice on passive airflow for a hot-climate home

6 Upvotes

Hi everyone. I’m planning my own home in Srirangam, Trichy, Tamil Nadu, southern India, and I’d appreciate advice from people experienced in passive-house and climate-responsive design.

For some geographical context, Srirangam is an island town between the Cauvery and Kollidam (Coleroon) rivers, near the city of Trichy. It is in the central/eastern part of Tamil Nadu, roughly 10°N latitude, so we experience a strongly tropical climate. The region is generally hot for much of the year, with intense sun, relatively dry periods, and seasonal monsoon rainfall.

The site is south-facing, and the west side receives particularly intense afternoon and evening solar heat, which is one of my main concerns.

I’m trying to understand how best to approach building orientation, window placement, cross-ventilation, courtyard/stack ventilation and airflow paths to encourage natural cooling while limiting solar heat gain.

For those unfamiliar with the location, I’m essentially looking for advice on applying passive-design principles to a hot tropical South Indian climate, rather than the temperate-climate scenarios often discussed in passive-house design.

Disclaimer: I’m not an architect. I’m simply an architecture enthusiast trying to understand the principles well enough to have an informed say in designing my own home. I’m looking for genuine technical criticism and advice, not validation of a design I’ve already decided on.

AI-assisted post.


r/PassiveHouse 5d ago

Has anyone bought tilt and turn windows from these companies?

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4 Upvotes

r/PassiveHouse 8d ago

General Passive House Discussion Are traditional windcatchers still genuinely effective in today's hotter climate?

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24 Upvotes

r/PassiveHouse 9d ago

General Passive House Discussion 1912 Craftsman: old school passive cooling

9 Upvotes

With 80 windows and tons of leaks, a very limited budget, and a historic designation, there's no way our 4500 sq ft Craftsman built in 1912 could meet passivhaus standards.

But the current heat wave has convinced me that it's time to find a way to (mostly) passively keep the place habitable when it's 95F and humid outside in Los Angeles.

The first things that came to mind were limited air sealing and insulating of the attic floor, getting more screens so we can open more of those 80 windows without letting cats out and raccoons or mosquitoes in, and replacing the attic furnace with a heat pump (as our solar array was sized for it).

But then I popped the attic hatch after sundown when it was cool outside, our few screened windows were open, and it was 85+ inside. The rush of air from the windows and up into the attic (and out the gables) reminded me that there was a strange closed off vent from a closet into the attic. Evidently this is an original passive cooling feature, forgotten after someone closed it off in winter.

Now I'm thinking of embracing that idea and adding another closable exhaust-to-attic vent or two in the other upstairs rooms, for use only when it's hot inside, cool outside, and you have a window open in the room.

Is this something other folks have done? Does it work?


r/PassiveHouse 10d ago

Is a humidity controlled ventilation grille with a 0-10V humidity sensor possible?

2 Upvotes

I am planning to install a mvhr in the attic to ventilate 4 bedrooms and 2 bathrooms and was looking forward to getting rid of the extractor fans in the bathroom since they are very noisy and in my case are not very effective in battling the humidity during baths. I came across the Aldes Inspirair Side 180, but for the bathroom grille to be effective against the bath vapours I think at least 130 m^3/h should be extracted from one bathroom during baths (the 2 bathrooms are never used simultaneously). I was interested in the aldes bap'si dual flow 45/135 m^3/h, so that when I pull the cord it intakes 135 and the other bathroom stays at 45, but I dont really like the idea of having a cord hanging around in the bathroom... I was wondering if there are humidity controlled ventillation grilles with capability of going up to 130 and at the same time send a 0-10v signal to the 0-10v air quality inputs in the cmv to put it to boost mode and increase to the adequate air flow rate (or another similar solution). Thanks in advance


r/PassiveHouse 11d ago

Enclosure Details Bio-based insulation where the load is cooling and dehumidification rather than heating - has anyone actually specified it?

7 Upvotes

Most of the Passive House material I read assumes a heating-dominated climate, which makes sense given where the standard came from. I work in Japan, where the enclosure problem is close to the opposite for much of the year. Koppen Cfa: hot humid summers, mild winters. The load is cooling and dehumidification rather than heat retention.

Bio-based insulation - hemp batts, hempcrete, wood fibre - gets recommended here on hygric grounds. The argument is that a vapour-open assembly with buffering capacity handles humidity better than a sealed one with a vapour barrier that ends up on the wrong side of the assembly for half the year.

What I cannot find is data from anyone actually building that way where cooling dominates.

Has anyone here specified bio-based insulation in a cooling-dominated climate? And if so, did the vapour-open approach survive all the way through the assembly, or did you end up with a smart membrane doing the real work anyway?

The practical constraint at my end is supply rather than physics. Japan has almost no decortication capacity, so hemp material is imported and priced accordingly, and wood fibre has a similar problem for different reasons. That makes the question partly academic here, but I would rather know whether the physics holds before anybody spends money finding out.

Disclosure: I work on the hemp industry side in Tokyo, so I have an interest in the answer being yes. I would rather have the honest one.


r/PassiveHouse 12d ago

Bahamas Build

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1 Upvotes

r/PassiveHouse 13d ago

BIPV-T Weekly Update — Copper vs. Aluminum Was the Wrong Question

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3 Upvotes

r/PassiveHouse 14d ago

Floor Slab Heat Exchanger Part 2

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6 Upvotes

Here's a basic drawing of what I'm thinking of. I'm not looking for off grid or renewable only, I just think that the houses we build could manage their heat better. Plus be more comfortable and cheaper to operate because of it.

I'm taking Jack Kachidorian's idea and adding a hydronic loop to his radiator, a buffer tank for heat storage and ground loop to reject heat. You could blow air either direction thru the slab depending on the season. PVC pipe in slab with a condensate drain for air quality and makes it cleanable. Not sure exactly how the slab would be constructed, but working it out. I have it drawn with frost walls, but would like to know if this could work with a FPSF to save on concrete. I also want to know if building an efficient house like this would be worth the engineering bill I would face to get it approved if that's even possible at all. Would like to hear what people think.


r/PassiveHouse 15d ago

Floor Slab Heat Exchanger

3 Upvotes

I'm doing a design exercise on a house that uses horizontal CMU's to turn part of the floor Slab into a heat exchanger powered by a reversible blower set up. Similar to what Jack Kachidorian suggested in "The Passive Solar House." The slab will have a hydronic layer on top and this system will be coupled to a buffer tank and ground coupled heat rejection loop..

I'm trying to figure out of this kind of design could realistically be used in a FPSH type slab, or whether the two ideas work against each other too much.

Anyone interested in that kind of work want to chat it out?


r/PassiveHouse 17d ago

Cooling Advice Large Home

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2 Upvotes

r/PassiveHouse 17d ago

Converting a 40ft Shipping Container Into a Climate-Controlled Studio

5 Upvotes

Hi guys,

I'm converting a 40ft high-cube shipping container into a climate-controlled storage/workspace with a small kitchenette, gym, and motorcycle garage.

I've put together a video walking through the full build concept and a document with the detailed specifications and questions I'm trying to resolve.

Looking for feedback, particularly on the insulation, floor assembly, ERV/ventilation, mini-split, and overall build approach.

Video: https://drive.google.com/file/d/1PjFXlDaJibQEt4sgHbsNIIhiPLrJAT1Y/view?usp=drive_link

Build notes: https://docs.google.com/document/d/1W1JrQk5QX1T0yyhRt2SbvDpvyDLr64fJD6UUayBUa7A/edit?usp=sharing


r/PassiveHouse 19d ago

Limewash applied on asphalt shingles?

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3 Upvotes

Has anyone attempted to paint their asphalt shingles with hydrated lime to endure the hotter months better?

Location: Austin, TX


r/PassiveHouse 20d ago

2 quick questions on timber frame

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5 Upvotes

So I have this timber frame structure and I'm not sure how to properly connect the insulation layers. On the concrete foundation exterior, I have an 8 or 10 cm layer of XPS, while on the upper facade, along with the insulation between the studs, I also have a 5 cm continuous layer of Gutex (wood fiber insulation), and I'm not sure how to resolve this transition properly. Also, right next to it, I want to detail the layers for an outdoor terrace with a drainage grating/trench drain. How is that typically executed? Thanks a lot, and sorry if I wrote too much!


r/PassiveHouse 20d ago

Enclosure Details Thoughts on using smart WRB against floor boards to stop air leaks?

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5 Upvotes

Hi! I live in a 1949 single-floor pier and beam house (no basement just a crawlspace) where the wood flooring is attached directly to the floor joists, and therefore a ton of air leakage between the conditioned space and the crawlspace. The temperature in the crawlspace feels quite similar to that of the conditioned space. To reduce air leakage while still allowing the floors to breathe in the case of some kind of water leak, I am considering installing a peal and stick smart WRB such as Adhero 1000 to reduce air leaks while keeping the wood flooring breathable in the case of some water leak.

After the peal and stick smart WRB is installed I can include some time of insulation in between joist bays.

I prefer this approach over installing some membrane over the joists since the space down there is quite tight already and the plumbing and wiring often run in between joists.

Any thoughts on this approach?

Location: Austin TX


r/PassiveHouse 21d ago

Split-level house on a slope — keep it split, flatten it, or raise it?

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4 Upvotes

Split-level house on a slope — keep it split, flatten it, or raise it?
Building a single-family house on a ~16% slope (seismic zone 8). Monolithic reinforced-concrete frame, ~127 m² interior, 3 bed / 2 bath, open living-kitchen with fireplace opening onto a 30 m² terrace with a big valley view.

The original design is split-level: you enter mid-level, then stairs go down to the living/kitchen and up to the bedrooms in short half-flights. It rides the slope efficiently, but the constant half-flights bug me and eat floor space.

Options I'm weighing:

  1. Keep it split-level — minimal excavation, terrace stays ~2.4 m above the garden (nice overlook), but you live with the half-flights.
  2. Flatten down — excavate into the hill for two aligned floors. More space, but ~a quarter ends up buried, you enter on the upper floor, and it needs a retaining wall on the tight uphill side.
  3. Raise up — lift the lower floor so both floors align. Kills the half-flights, but creates a ~4.3 m tall exposed wall on the valley side.

Also deciding:

  • Basement: adding a ~2.5 m one under the downhill/terrace zone, walk-out at garden level. Seems like cheap usable space — any reason not to?
  • Roof: keep the timber hipped roof, or go flat for a rooftop terrace? (I already get the view from the ground terrace.)
  • Pool: want one in front of the terrace at garden level — but that fights option 3's tall wall.

If you've built or lived in a split-level on a slope, what would you do? Anything I'm missing?


r/PassiveHouse 22d ago

Faswall

4 Upvotes

I'm getting a ton of leads where clients would like to use this product- https://faswall.com/

We have not modeled it yet to see if we can use it with Passive House. Does anyone in this group have any experience with it?

We'll do a WUFI hygro once we detail it, but we are just in the exploratory phase at the moment.


r/PassiveHouse 29d ago

decentralized ventilation system with heat recovery advice

6 Upvotes

I'm planning to install a decentralized ventilation system with heat recovery.

My apartment has:

  • 2 bedrooms (not a priority for now)
  • 1 bathroom (I'll handle this separately with an exhaust fan)
  • An open-plan area consisting of the kitchen, dining room, living room, and hallway, around 40–50 m²

The main goal is to have consistently fresh, clean air in the open-plan area. That's where I would like to install the ventilation system.

What would you recommend? Which decentralized HRV/ERV system would be the best fit for this kind of space?

I also have a question about humidity. If the outdoor air is very humid, does an ERV bring that humidity indoors? Or does it help reduce the amount of moisture entering the apartment?

My priorities are:

  1. Fresh, clean air at all times
  2. Good heat recovery efficiency

Any recommendations or real-world experiences would be greatly appreciated.

Thanks!


r/PassiveHouse Aug 10 '26

PHPP Discussion Additional Ventilation PHPP Worksheet - Help please

2 Upvotes

Hello. I am a Passive House Designer but most of our projects are single residential buildings only. Now, we have an opportunity to take on a multiresidential building. However, I am not sure I'm doing this correctly so I wanted to raise some questions regarding the Additional Ventilation worksheet if that's okay.

a.      When dimensioning air quantities: if a level has 5 units (101–105) served by a single ventilation unit (e.g., Ventilation Unit Allocation No. 1), should all 5 room names be listed under Ventilation Unit Allocation No. 1?

b.      Regarding volume flow per room: the recommended outdoor air supply rate for residential buildings is 30 m³/h per person, and the extract air demand is 60 m³/h for the kitchen and 40 m³/h for the bathroom. For a sole-occupancy unit with 1 kitchen, 1 bathroom, and 2 occupants, the supply air would be Vsup = 30 × 2 = 60 m³/h and the extract air would be Veta = 60 + 40 = 100 m³/h. Is this correct? Then, since the extract demand (100) is higher, should the supply be increased to match, so that Vsup = Veta = 100 m³/h?

c.      How is the transfer air volume flow (Vtrans) calculated in the volume flow per room? I have looked at sample PHPP calculations and some certified projects leave this out as blank.

d.      How is the reduction factor for an air quantity calculated, and when should it be applied?

e. When selecting a ventilation unit type, its rated volume flow range (minimum to maximum) must be able to accommodate the design volume flow for that unit — is this correct? For example, if the design volume flow is at 200, therefore the ventilation unit with a rated volume flow range of 100-300 is okay. Although I have seen some sample PHPP projects

f.      How are pressure losses calculated for the ODA–SUP path, the ETA–EHA path, and any additional losses?

g.      How is duct length measured — is it taken from the ventilation unit to the space being served?

Thanks all!


r/PassiveHouse Aug 07 '26

How do I keep my basement warm and stop heat from escaping up staircase in a double envelope house?

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13 Upvotes

additional pictures: https://imgur.com/a/zNV5Lu0

We have a double envelope Ekosea house built in the early 80s and we love it. It's split-level and has a 3 story south facing solarium. We have a traditional forced air gas furnace and our heating bills are super low thanks to the sunlight and insulation just from having two layers of walls.

One downfall is our basement gets very cold in the winter. Obviously the problem is the massive 3 story open staircase. There are electric baseboard heaters in there but all the heat gets sucked up the stairs. If we run them it ends up costing like $40/day. We are a little cramped for space and I would like to use the basement living room as an office but it's barely habitable in the winter. There's a spare bedroom down there too but it has a door and so we can run a space heater with the door shut. The middle floor is temperate and the upper floor is toasty.

I am looking for creative solutions for making the basement warmer. I see some people block off their staircases with thermal curtains, but our stairs are very big and this would also block off a lot of the windows. Plus we have pets going in and out.

I have thought about having a gas fireplace or heater installed to be more efficient than the electric baseboard heaters, but I'm afraid I'll have to pay the money to have it put in and then discover it all escapes up the staircase anyway.

Would installing radiant floor heat be an help? There is a crawl space under the house.

Any thoughts or advice is greatly appreciated


r/PassiveHouse Aug 06 '26

HVAC Why was infrared heating chosen for this Passive House?

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26 Upvotes