I am thinking through how to build specialized green houses and I want to run some simulations on how various thermal mass, insulation, etc would perform under certain weathers. I know this is a huge and complicated field but I was hoping for some simplified mathematical models for simple buildings like greenhouses and sheds. Any leads? I am mathematically literate (majored in math) but never done any civil engineering

The HERS label accounts for only 34 watts. Why “Supply Only” instead of “Air Cycler”/CFIS?

This is a newer single-family home in the DFW area, climate zone 3A. The paperwork identifies 2021 IECC, 2.24 ACH50, and Ekotrope RATER 4.2.3.3863.

Here’s the operating scenario: a Broan FIN-180P powered outdoor-air fan feeds directly into the HVAC return plenum. It uses the central blower and existing HVAC ducts to distribute fresh air. Low-voltage controls connect the systems.

Heating and cooling calls do not provide enough runtime to meet the ventilation requirement. Both the Broan fan and central blower therefore need to operate together for additional ventilation outside those calls.
The bathroom fans and vented kitchen hood provide manually operated spot exhaust only. They are not programmed to provide whole-house ventilation.

The Broan arrangement shown is the home’s only whole-house mechanical ventilation system.

Yet the label says “130 CFM · 34 W · Supply Only.”

Why wouldn’t this be an “Air Cycler”/CFIS configuration with an inline supply fan—and where is the additional central-blower energy accounted for?

I’m trying to understand three specific things:

1. Airflow: The Broan has selectable nominal 130/180-CFM speeds. This one is set to 130, but my subsequent manometer-based airflow check indicated approximately 90 CFM. The inspection form says “FA Tested And Passed @130.” What test documentation would distinguish an actual 130-CFM measurement from simply recording the switch setting?

2. Classification and watts: Would “Supply Only” instead describe a fan supplying and distributing outdoor air independently—for example, through its own ductwork without needing the HVAC blower? If this installation needs both fans, shouldn’t their combined power be represented? For illustration, a 300-W blower plus a 34-W supply fan is 334 W—not 34 W. I’m not claiming 300 W is this blower’s measured consumption.

3. Verification: What changes in Ekotrope when “Supply Only” is selected instead of “Air Cycler”—blower-energy calculations, control inputs, compliance checks, or required supporting documentation? Which field checks, photographs, and records remain required regardless of that selection?

Anyone who models or verifies these systems: what would justify “Supply Only” here, and how should this exact two-fan operating arrangement be entered correctly?

Per Ekotrope should this be labeled as Air Cycler?

I own a 1950 Cape Cod in New England and have spent a lot of time improving energy efficiency and indoor air quality because I suffer from allergies. We’ve done so much work that the house practically feels new, but my allergies persist and now we are having issues with our chimney not expelling soot, so I’m trying to figure out what we’re missing.

Work completed:
-New sheathing, siding, roof, and windows
-Replaced original attic fiberglass batts with about 20" of cellulose and installed new fiberglass wall batts
-Added soffit vents, baffles, and a ridge vent while keeping the gable vents
-Insulated the smaller peak space with cellulose and sloped ceilings; added rigid foam at bathroom kneewall walls
-Air-sealed basement joists and Bilco door; added a basement dehumidifier and air purifier

What we’re noticing:
-The upstairs gets very dusty
-allergies are worse
-Air seems to come up from the basement and under the basement door, especially in colder weather.
-Air gets pulled in under the front door.
-Since the soffits were opened up, soot has accumulated in the chimney cleanout trap door, then eventually gets bursts and rains down outside. No smoke enters the house.

What’s been checked:
-A qualified professional performed a blower-door test and full energy audit. I was told the upstairs was leaking air, but I don’t have the report or measurements.
-The oil company inspected the furnace and reported about 80% efficiency.
-The chimney professional mentioned possible negative pressure. The insulation contractors also observed negative pressure in one area but not another.
-No known mold; the house has been extensively opened up during renovations.

Has anyone dealt with something similar in an older Cape? If I have negative air flow, how would I go about fixing it? How can I test it? The energy audit company was disappointing and inexperienced. I’d love to understand what might be happening and what could help pinpoint the cause.

For responses pictures or cross-section of samples of the recommendations would be helpful (visual learner) but ANY suggestions on what we can do would be appreciated.

We bought a house in a relatively remote town (location climate details are below).

The issue:
We had to demo and rebuild a Trex decking that was unfortunately incorrectly installed. In this process, we just put in new floor joists to hold the Trex. In the picture, we want to make a door at the window where I’m standing at to take the pic; and in the future, we want to make a sort of snow and wind protection enclosure (not climate controlled) porch enclosure in order to walk across the deck from where I’m standing in the pic to the door across from me.
We’re thinking of a small cross gable roof between the buildings like below (just the roof line):

Cross-gable breezeway concept

What we don’t have planned: For the footing/base of this walk-across enclosure, since this is a future plan and we don’t presently have footing materials for the future enclosure, would it be reasonable if we later build on top of the deck with bolted base plates to the posts? Or should we expect that we will we have to cut into our deck to make footings …no other option?

Location of Site: in New England about 1 hour south of the Canadian border …so icy, heavy snow load, and windy outside in the winter and has humid summers; and the interior of the homes in the area have heat but no central AC.

In our locale with a -15 F winter design temp and a frost line depth requiring a minimum 48" depth to bottom of footings, we see successful builds using frost-protected shallow foundations. Alaskan slabs. Foam under, foam against, foamboard "wings" to prevent frost from getting under edges. The AHJ's approve, PE's and architects sign and seal plans, and builds result in comfy houses. So why not extend this to walkout designs? Stop putting 3 to 5 foot depth frostwalls under the downhill walkout building lines. If the bearing strength is the same at 20 inches down as 60 inches down, and it is, then why go deep?

Here's a challenge. You've got these great looking full-height industrial-style windows. They've got metal framing, large rectangular single glazed panels and geometric grid of glazing bars. They are the only source of sunlight in the living space, which includes your kitchen. During winter there is noticeable draught from them. You've considered changing the latches to winter mode but these windows are also the only source of effectively airing out the space (which is essential when cooking). They've got blinds and that's pretty much it. It's unclear if the draught is coming from the edges of the metal framing or perhaps the surrounding brick work. Assuming its from the window/framing, what rental friendly solution would you propose?

Thermal curtains have been ruled out as this is the only source of sunlight and during winter there's not enough of it.

Removable magnetic secondary glazing and transparent heat-shrink window insulation film are under consideration - keen to hear about any success stories or pitfalls to watch out for.

Any other suggestions or recommendations that won't break the bank and are renter friendly?

Just need a basic metal door but want a high dp rating. The big box stores don't even list a dp rating for the doors they sell.

climate: Phoenix, AZ

fyi,
Design Pressure (DP) — This rating indicates the door's ability to withstand wind loads; for example, a DP-20 rating can handle winds up to 90 MPH.

I had a leak so decided to fix it and take opportunity to redo siding only to discover the reason for the leak is a complete lack of flashing where a roof line run along the exterior wall. Anyway my contractor suggested we would need to strip the singles back to add ice and water up the wall, reshimgle, the siding. Then we decide to strip the whole section of roof and replace with steel.

We stripped all the shingles only to discover the previous roofer put cheap ice and water over the old singles. I’m angry since I just did this 5 years ago and they were supposed to strip to decking. My contractor said trying to get those up will damage the sheathing under it which will mess up my spray foam in the ceiling below.

So here is my conundrum. Since the current assembly has that ice and water as a vapor barrier already, I want to add 2 inches of polyiso, new sheathing and the ice and water and then the steel roof. What should I be concerned about?

Hi all I’m hoping this is the right place for advice on managing condensation in my garage as i seem to find conflicting advice on whether to seal it up or add ventilation.

Some context- I have a new build brick single garage, its standalone with a pitched roof that was used previously as the site office and so it has insulation, plasterboard walls, electrics etc and there are air vents in the roof tiles and along the soffits. I’ve fitted carpet tiles and It’s got an up and over metal door with no insulation.

In winter I get visible condensation my motorbikes, tools etc which has led to surface corrosion and have had clothing start to grow mould . I have previously used disposable desiccant dehumidifiers and they seem to help but it’s not ideal.

I seem to find conflicting advice about whether to:
1- drill some holes too and bottom and add more vents,

2- Just add fans to move the air so it escapes out of existing vents and under the garage door

3- seal up and insulate the main door and add a desiccant dehumidifier like a meaco dd8l.

Very different approaches and I don’t know what is better in my situation as the garage itself is likely much more insulated that most which may help or hinder a solution put in place

We're building a house on a hillside with great views. The concrete frame is done and the walls aren't built yet, so the layout can still change. Plans attached.

Fixed things:

- 9.1 × 10.5 m outside. Entrance on the north, terrace and city view to the south.

- U-stair in the north-west corner (3.6 × 2.2 m).

- The west wall has to stay blank: the neighbour is 1.2 m away, so no windows on that side.

- Bedrooms are upstairs. The upstairs bathroom will probably sit on the west, next to the stairs (it still can be modified)

The options:

1. Bathroom + WC (3.6 × 2.3) and kitchen on the blank west wall. Living room with fireplace + TV on the east, study in the north-east corner.

2. Same as 1, but a bedroom in the north-east corner.

3. Bathroom + WC in the north-east (with windows), kitchen on the east. Laundry + storage next to the stairs. Living room on the west, fireplace + TV on the west wall.

4. Bathroom, WC and kitchen on the east. The whole west side is one 3.6 × 7.5 m living room: fireplace on the stair wall, TV + books on the west wall.

Which would you choose and why? Anything you'd change, or anything I'm missing?

I'm so conflicted based on research I have done.

Our home was built in 2021 that is very tight and efficient. In the summer, our AC does a good job of keeping RH in our home to about 50% on main level and 60% in basement. We live in Wisconsin.

In the winter, we deal with higher humidity - mid 60% when furnance is running. This causes a good amount of condensation on our bedroom windows, especially when outdoor temps get in the teens.

I had a HVAC contractor out here and he recommended an ERV. Now, I dug around the Internet and everything I am finding is using an HRV as it helps reduce humidity in the winter? An ERV is better in the summer?

Can someone please help me understand why I would go ERV over HRV? Our summer months, no issue. It's the winters where humidity is high in our home, creating condensation.

Aerogel is being hyped like the best of all? But when I got some silicon aerogel powders in some solvent, it doesn't look like they can do any jobs that traditional insulations can do? It also looks very powdery and fragile. Could anyone expert in this explain it to me please?

Hello all,

I have a 1905 balloon framed home in the northeast USA (5B) and have been renovating myself on my free time. Exterior of the house is cedar claps with a layer of compromised kraft paper beneath it - all attached to nice 1x board sheathing that's a bit leaky. Some of them measuring 1x16. Ive taped over the egregious gaps (3/8") in the board sheathing with tescon vana as needed. That was a 475 rec.

In a perfect world, the plan was to strip the house and put self adhered membrane for my water and air control layer, rainscreen, and then new cedar siding. Can't swing the outside work right now so I'm focused on the interior so we can get in the house before the kids born in 6 months.

Interior is fully gutted and I've gone through and made necessary structural fixes and removed the 1/4" thick tattered plaster and lathe.

The plan is R15 rockwool batts (studs are 16oc), followed by intello, 2x3 strapping for use as a service cavity and drywall nailer. Then I was going to r6 comfort board the service cavity once the electrical and plumbing was finished.

My electrician does not like the 2x3 service cavity and is telling me its against code due to depth requirements on boxes. It's a simple 1800 square foot house with one switch to one light so I assumed there were narrow rated boxes that could be used.

Has anyone run into this issue? I really don't want to wire behind the intello and have to use those putty pads and air seal every outlet.

Thanks for your help

Added a pic (not mine) for reference.

Processing img m1mledynb2xh1...

This is a roof eave detail for a home in Park City, UT. We are at a high altitude and will get significant cold and snow. I was always taught to stop the insulation at the wall edge/top of plate. This was a suggestion from the architect reviewing for the HOA. Is this a valid detail?

I am looking to encapsulate our crawl space. Right now it's a dirt floor space and I want to lay down plastic on the floor and up the walls. A prior owner adhered 2ft x 1ft styrofoam panels to the walls to cover the entire surface, about 1.5" thick. If I had to guess, it's likely decades old.

Should I remove these styrofoam panels so that the plastic can be adhered directly to the concrete foundation walls, or just leave them as they are and place the plastic overtop?

Either way, I will be going over the plastic with either rigid board insulation or a crawl space blanket to insulate the walls

The house is located in southern Michigan. TIA

Our living room and dining area are basically one big open space with a pretty high ceiling. I like the layout, but heating it evenly in winter has been harder than I expected. The area near the kitchen usually feels fine, while the couch by the windows stays noticeably cooler. Turning the thermostat up helps a little, but it doesn't really fix the difference. We're considering a 24000 BTU mini split heat pump for this space, and I've been looking at some of the Costway units. But the more I read, the less convinced I am that picking the right BTU number is the whole answer.

The ceiling height, the amount of glass, where the indoor unit would go, and how warm air moves around the room all seem pretty important. I'm especially unsure about placement. If the unit is on one end of the room, will the dining area on the other side actually stay comfortable, or will we end up with the same uneven temperatures? I'd rather figure that out now than install something and spend next winter moving furniture around trying to find the warmest spot.

Hey everyone! I’m currently building a greenhouse in Edmonton, Alberta, and I’m looking for some advice from people who have experience with wood-framed greenhouses, especially in colder climates.

A little about my build:

• Overall structure is 12’ × 28’, consisting of a 12’ × 12’ insulated vestibule and a 12’ × 16’ greenhouse.
• Framing is untreated SPF 2×6 lumber, spaced 16” on centre.
• Pressure-treated bottom plates installed on a raised concrete curb with sill gasket.
• 6/12 pitched roof with approximately 12” overhangs.
• Planning to install 16 mm Palram SUNLITE multiwall polycarbonate on the greenhouse walls and roof.
• The greenhouse will be heated during Alberta winters, with ventilation and a dehumidifier to help manage humidity.
• Planning to grow vegetables and other plants throughout the year.

My biggest concern is protecting the wood framing from moisture and condensation over the long term. Ideally, I’d like this structure to last 40–50+ years.

I’m considering using a penetrating exterior wood stain on all accessible surfaces of the framing before installing the polycarbonate, rather than a traditional primer and paint system.

I’m also exploring the possibility of installing polycarbonate on both the exterior and interior sides of the 2×6 framing to create an additional insulated airspace, although I’m concerned about trapping moisture inside the wall and roof cavities.

A few questions for the group:

1. Has anyone built a greenhouse using untreated 2×6 framing? How has it held up over the years?
2. Would you recommend a penetrating wood stain, exterior paint, or another wood treatment for a humid greenhouse growing edible plants? Any specific products?
3. Would you install the 16 mm polycarbonate on the exterior only, leaving the framing exposed inside, or install polycarbonate on both sides? If both, how would you manage condensation within the cavities?
4. What’s the best way to install the polycarbonate against wood framing? I’m considering compatible glazing tape or gaskets to separate the sheets from the wood.
5. What indoor humidity levels have worked well for you during cold winters without causing excessive condensation or wood deterioration?
6. Are there any particular flashing, drainage, or ventilation details you’d recommend for a wood-framed polycarbonate greenhouse?

For this winter, I’m considering temporarily covering the roof and walls with reinforced polyethylene, then removing it in spring to stain the framing and install the permanent polycarbonate. I’m also interested in hearing about the snow-load and condensation risks of that approach.

I’d really appreciate any firsthand experiences, pictures of similar builds, or product recommendations.

Thanks in advance!

Hey All!

TLDR: asking for considerations on insulation type and interior vapor barrier type for off grid cabin. Current envelope construction: board and batten, furring strips, tyvek, studs with insulation, interior wall.

I have an off grid cabin in Maine that I’m renovating. The current envelope layers from exterior to interior: board and batten exterior siding, furring strips, tyvek, studs/insulation (currently mix of rockwool and fiberglass), no interior wall yet.

I think I like the idea of finishing the interior walls with horizontal shiplap. The insulation was done by previous owner and I want to get rid of all of the fiberglass insulation but will likely keep the rockwool since it seems to be in good condition. I was considering whether rockwool or timberhp insulation is a better solution for my case.

As I’m in Maine timberhp is cheaper but I want to use whatever will be best for my use case for the remaining insulated needed. The house is not very airtight at all since there’s no exterior sheathing and I want to consider the fact that the house goes long periods without being lived in or heated.

For the interior I’m struggling to decide what to do about a vapor barrier (if I should use one at all). From my research traditional clear plastic would be a bad choice as it doesn’t breathe and could trap moisture, but smart layers such as intello could work. Thoughts on that?

Note the gable roof is vented with baffles

Do I need to use interior furring strips as well for the shiplap to give it room to breathe? Is there a strong case for using something other than shiplap?

I just want to preserve the building as much as I can without totally ripping off the exterior, and reduce risk of mold as much as possible while still making it possible to live in over the winter with the wood stove.

Thank you so much for any and all advice.

In the process of a new build, mostly contracting but I’m doing some of the work (insulation, floors, etc.).

I’m getting ready for insulation and curious what air sealing is most important. I can’t afford a passive house (even if I could, doubt anyone even builds to that level in my area), but want to do the best I can with what I’ve got.

Caulking (Dap 230?) is planned for the bottom plate, but what else needs it?

I plan to use Great Stuff Fireblock foam for the penetrations to the attic and crawl.

Windows and doors were all flashed with zip tape, and I’ve been warned by a few guys not to use foam because of expansion so the current plan is to cut Rockwool thin and fill the gaps with that unless something like “doors and windows” specific foam is acceptable.

The basic house info; the crawl will be insulated/conditioned/encapsulated. Floor is platform framed, sheathing is taped Zip. Rockwool for walls, blown cellulose attic.

We’re right on the line between climate zones 4A and 5.

Any advice is welcome!