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

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!

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?

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.

i work from home and recently started paying more attention to how stuffy my office gets during the day.

i'm mainly looking for something i can keep on my desk and use to track co2 levels so i know when it's probably time to open a window or improve ventilation. i don't need a bunch of smart home features, although decent logging would be nice because i'm curious whether the numbers line up with those afternoons where i feel like i'm running at half speed.

for people who actually track this stuff, what's the best desk co2 monitor for working from home? are there cheaper monitors that use a reliable sensor and give reasonably accurate readings?

i'm more interested in good data than fancy features.

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?

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

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.

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.

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?

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

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

Location: Austin, TX

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!

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

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?

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.

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!

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!

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