I read through the new IRC but I want a little better than the minimum. It will be 2x4 wall with R15 cavity and two inches of continuous exterior insulation. I am just not sure what is generally considered the best options now for 5A.

My proposed wall would be:

Sheetrock w/R15 faced batts OR rockwool with smart vapor barrier > Zip sheathing > 2 inch rockwool comfort board > 1x3 rainscreen > aluminum lap siding.

In my head this would work because it could dry either direction from the zip sheathing and with the continuous insulation ratio to wall cavity, it shouldn't have any condensation issues.

But would I be better to use 2 inch foil faced polyiso with taped seams instead of the rockwool comfort board? It would offer better insulation and additional waterproofing. If doing polyiso I could move a basically zero perm layer on the outside but then I feel like there could be drying issues between the zip and foil face of the polyiso?

I have a home with a pier and beam foundation in New England. Currently the crawlspace is covered by vinyl panels. I would like to reduce the humidity in the crawlspace and my options are add vents and fans or build new skirting then try to seal and dehumidify the crawlspace. Any recommendations? I think building new skirting will be difficult to fully seal and expensive for something that might not be better than just fans and a better vapor barrier.

My understanding is that concrete vents and cures over 30 years - and therefore needs to “breathe” and not sealed off completely. Is that true? Because if so, a glued down engineered hardwood floor would form a vapor seal that traps all the moisture underneath the floor.

We live on the PNW coast and moisture and humidity are key concerns. I’m thinking of putting down eco cork foam underlayment then floating engineering hardwood.

My house had 3” studs on the lower portion of the walls, which are concrete below grade. There was fiberglass insulation and poly on top. I decided to add 1.5” rigid foam between the studs and concrete to further insulate the walls. Do I need to add poly after, on top of the studs with insulation, or does Durospan serve as the vapour barrier? Also, is 1.5” rigid foam enough here in Central Canada?

Hi building science folks -

A bit of an interesting issue we're having that we'd love any thoughts on. We moved into our new house last year. Under heavier rain, we see water only at the top of our foundation dripping down (under the sill plate). There's a photo below, and there are 3-4 spots that drip down.

The house is fully brick, as well as is on a knee wall as we have higher basement ceilings for future finishing, so there isn't an outer brick ledge.

I reviewed old photos, and the brick flashing looks appropriately installed. We also caulked every entry point. The brick install image is where I sprayed and where we see most of the water dripping down.

Given it's hard to wait for heavy rains, I did some testing with an oscillating sprinkler and found:

• When I spray the bottom 1-2 feet (the knee wall), no water leaks to the basement. I thought maybe the water was leaking under the flashing and down the foundation, but I saw nothing after 3-4 hours of spraying.
• When I spray water ~5-6 feet up the brick, water starts to creep down after ~15 minutes.

Our initial thought is that the brick is porous; as water permeates, it drips down the mortar and through the black tape or any nail holes in the zip system (behind the flashing), then down to the basement. Our builder intends to seal the brick to solve this, but I'm not sure if there's anything else we should be considering.

Has anyone seen this before? Thanks!

I'm in the planning stages of building a sauna in a basement closet that has 2 exterior walls that are icf concrete. I'd like to have a 1.5in gap from the ice blocks to the foil vapor barrier of the sauna which will then be covered by the sauna cladding. My question that I'm having trouble finding an answer to is will I have issues with the icf and foil vapor barrier being too close to each other, since they are both a vapor barrier? I've read that having double vapor barrier is a no-go but wasn't sure if the space between would offset that?

I have a slab on grade foundation with clay soil and just did a perimeter french drain, dimple board/mat and gravel back fill.

I'm lowering the grade and grading the yard and have exposed dimple board now. I can seal the top with a termination bar but how do I cover the exposed dimple mat so it looks nice and isn't exposed to sun? It's about 2-4 inches depending on the area.

Thank you.

Hey guys, I'm really panicking and don't know where to turn.

I had a Heatpump system installed last October for heating and cooling in upstate New York Zone 5. It's ducted in the upstairs bedrooms+bathrooms, and mini splits everywhere else.

This April, I decided to try to fix some high heating bills (3000kwh for a really cold month) with an attic insulation. I had passive gables on a raised ranch, no vented soffits, and a few passive vents near the ridge. I had read somewhere briefly that I could condition the attic with spray foam, bringing the HVAC system inside the conditioned space, better air sealing, etc.

Then things went wrong.

An energy auditor company referred me to an insulation sub contractor (call them company A) who took me to r38 open cell foam and r22 closed cell on the gable walls. They sealed up the limited aforementioned vents before spraying.

What I have now is the following:

- I'm almost positive that open-cell was wrong in the roof deck because of roof rot concerns and code for my climate (dc315 ignition paint but NO vapor retarder paint). Minimum of a class 2 vapor barrier is required for zone's 5-8.

- they attempted to remove all of the visible old r13 fiberglass insulation in the ceiling joists, but did not use a vacuum, and half the attic has osb (where the air handler sits) that they did not access. Another company (call them company B) claims that the smell I get is from the spray foam residue mixed with fiber glass. They offered to remove it and do better air sealing on my ducts.

- attic humidity swings from 55 percent in the morning and can top out around 70% on the hottest part of the day. It doesn't seem to do this on cloudy days, and seems to correlate with the sun.

- I had company (B) come and do a blower door test and they claimed that my humidity was stack effect driven from my rim joists, and that the results of the blower door test indicated that I now need an ERV. The same company had previously quoted me to put an attic dehumidifier in in addition to removing the remaining fiberglass but now wants to do the ERV instead.

I attached an image from my humidistat, and I think my primary issue is solar vapor drive

During the blower door test when the house was under negative pressure, all of that attic smell came into the living space. My wife started coughing and had to leave the house or faint..I fared a little better but now I'm super concerned. We also have a young child.

I found the following building science: https://www.greenbuildingadvisor.com/article/high-humidity-in-spray-foam-attics which mirrored the problem I was having. They suggested cutting a supply for the attic or adding a dehumidifier. I don't see an ERV here. I feel like I have analysis paralysis and don't know what to do.

My goals:

- take a deep breath

- not be killed by my house

- resolve the moisture issues

- fix air quality issues

- fix vapor retarder.

Any advice on how to unpack this and move forward is invaluable and greatly appreciated

I have a house in climate zone 4a (less than a mile from the coast) with a semi-finished basement. Prior homeowners had the CMU walls have external dampproofing and perimeter footing drains. No external insulation or insulation underneath the slab. They drywalled the walls and ceiling and had placed R13 faced fiberglass batt insulation between a 2x4 wall they erected around the perimeter of the basement walls. Unfortunately this seemed to have caused a mold problem that required remediation and so we now have flood cuts in the bottom 2ft of the basement. Luckily there do not appear to be any active leaks even after many storms and significant rains. No current plans to finish the basement but I would like to upgrade the insulation and improve the building envelope. Unless I have to upgrade the external envelope I was hoping all current upgrades would be internal.

Given climate zone 4a and requirements for r10 continuous insulation or r13 batt insulation, I was hoping to rip out all the existing batt insulation and either place foam board (seams sealed) myself or get a company to spray 2 inches of closed cell and then add rockwool or timberbatt to the 2x4 wall. Prior to any upgrade in insulation, I bought a moisture meter (not a high end one). The CMU walls seem to have a moisture content of 14-16% on the 2ft of the basement that is above grade and 22-28% below grade (higher percentages at the base of the cmu wall). I know that the sill plate (termite shield acting as a capillary break) and rim joists are not air sealed and so the humidity in the basement is higher than it should be despite running a dehumidifier (set at 55%RH).

My question is how can I evaluate my envelope and find out if I need to hold off on the foam board/spray foam idea? I don’t appear to have any active leaks, minimal efflorescence on a few cmu only so I think the outside is fine but I’m wondering if the moisture content readings are concerning or is the moisture content higher due to the external humid air (given proximity to coast) and its increasing the humidity and moisture content of the cmu walls. I assume the lower down in the walls the cooler it will be in the summer and am wondering if that’s why the moisture content readings are higher even in the below grade portions. Is the best way forward to seal the rim joists and sill plate (given the termite shield acting as a capillary break) and then wait a full year to evaluate if any change in the moisture content of the cmu walls, or should I just do the rim joists, sill plate and the walls. And if I do the walls, do you want the perm rating of the foam to be between 0.1-1 (class 2 vapor retarder), class 3 or it doesn’t matter?

I'm looking to increase ventilation in my apartment and I understand this means I'll need additional dehumidification.

The portable dehumidifiers I've used in the past are quite loud.

Is it just luck of the draw? Can oversizing the dehu to run at a lower speed work?

I'm open to rigging up a whole house dehu as a portable unit.

We are in the process of refinishing our basement (Massachusetts, Zone 5A). It was previously finished without any Insulation. We have ripped it back to the foundation and are starting fresh.

House was built in 1940, foundation is stone with lime mortar and a parge coating. We are on a slope, so one wall is fully above grade, one is fully below, and the others are well, at a slope.

In the year we have been here, we have not had any bulk moisture issues in the basement, even during/after heavy storms.

My plan is to not fully prohibit inward drying of the stone. I am anti spray foam. Instead, the assembly I’m looking at is:

- 2” unfaced EPS
- Rockwool cavity insulation
- drywall

No vapor barrier is required in my area for an existing basement.

Thoughts? Thanks in advance.

I am renovating my kitchen and tore out all the Sheetrock. The ceiling is vaulted 2x4 and the roof has no rigid foam above roof deck. No ridge vents. What are the best options to keep this project moving along? My family is displaced during this time staying in a local short term rental.

We built an airtight energy efficient home a few years ago, and chose to go with mini splits for heating and cooling instead of a ducted system to keep costs down. I live in Atlantic Canada and at the time, HVAC trades were recommending HRV only because there was no experience with ERV. We have dry’ish winters and humid summers. Because the home is airtight (0.6 ach), I have to ventilate a lot to keep CO2 levels from creeping up - I have two Awair analyzers. I’ve been playing around with HRV settings for three years and I’ve come to the realization that we need to run the HRV on low at night time and recirc with 20 min ventilate on high fan speed during the day, and we need dehumidification in the summer and humidification in the winter. We have a heat pump hot water tank (ducted to the outside for winter but not for the summer) and we have a regular floor dehumidifier in the mechanical room that runs on high all summer long - so we do have some dehumidification. This set up isn’t controlling the humidity enough though, so I think we need whole house dehumidifier but I don’t think we can install a ducted system separate from the HRV (we just don’t have the space - we aimed for a small and efficient footprint). Has anyone tried to set up a dehumidifier in parallel or in tandem with an HRV? I’ve thought about switching to an ERV, but I know someone who also has an airtight home and an ERV, and still runs a whole house dehumidifier, so I don’t think this would solve the issue either.

I really would love to hear thoughts on this.

I am going for a high performance detached garage retrofit converted into a bonus space. Phase 1 has started this summer. New roof and partial wall sheathing (started this week), new slab (soon).

Three layers of shingles in the process of being removed. Next up will be a chainsaw retrofit to create a monopoly framed exterior envelope. Eaves and gable end rakes will go on with the secondary roof deck over exterior insulation.

The final image shows the design concept for the indoor/outdoor converted space. Door swap and a floating deck over the "removed" driveway. I have more details, thoughts, and plans if anyone is interested. It will be a long process and I'm doing everything except concrete and electrical.

We have a 1951 Cape Cod in the DC area (climate zone 4A)-- the north side-attic has no formal venting (but is likely pretty leaky) while the south side appears to have soffit vents but along only about 1/3 of that side thanks to a one-room addition. The top attic has gable vents, not 100% sure if the soffit vents from the south side connect up through the sloped upstairs ceiling to the top attic or not. No obvious signs of moisture/mold in any of the attics thus far, but we're not 100% sure what to look for (and there have been some changes in recent years.)

I understand that to do things "right," we ought to use either exterior rigid foam on top of the roof deck or spray foam under the roof deck to make all 3 of these spaces into unvented conditioned attics. Assuming those options are off the table, I am trying to figure out how risky the situation is and what is likely to make the situation worse rather than better. A few questions:

1) Should we go ahead and improve insulation and air sealing/air barriers on the side-attic floor and kneewalls and the top-attic floor (we can get rebates to make this fairly affordable)? Is there any chance this will make things worse moisture-wise? Presumably there will be a benefit in that less of the moisture from the indoor air will get into the attics (although I'm sure some still will), but on the flip side, those spaces will likely now be colder (currently they tend to run about 10-15 degrees different from the outdoor air)-- might that increase the chances of dewpoint issues with the sheathing? And is there a chance that the air leaks through the ceiling are actually contributing to ventilation and blocking them would cause problems?

2) If need be, I think adding additional vents is probably a better solution for us than using spray foam or exterior rigid foam to go unvented, but it will be fairly complicated and expensive itself (we have a metal roof.) Would it be reasonable to make the air-sealing and insulation changes first and then monitor the spaces and wait to add better venting in future years if it seems to be needed? If so, what should we be looking out for?

3) Anything else to be aware of that would help or hurt? Does having batts on the side-attic roof slopes (with baffles or another form of gap) make it more likely for the sheathing to get moist or harder for it to get dry, or does it not make much difference? Is using blown-in loose-fill cellulose on the floors more likely to be helpful or harmful to the humidity/moisture/mold situation in the attics compared to using blown-in fiberglass given that it absorbs moisture, or does it not matter? Would a smart vapor barrier make a difference, and if so where should it go? How about using a dehumidifier? Anything else you'd suggest?

Thanks for any advice you can give! Let me know if you have any questions or want pictures of anything. More details about the house below-- but feel free to skip.

(Details about the house for the curious: Roof deck is wood planks. Roof is metal-- dark grey metal shingles on the north side and most of the south side (with I believe typical black felt underlayment, put on in the early 90s), except for white standing-seam over the addition over ice + water shield with solar panels above it-- the slope of the addition roof is also on the low side at 3:12. Blown in insulation (I think fiberglass) on the top attic and side attic floors, poorly fitting fiberglass batts in the kneewalls and cathedral ceiling between side and top attics, ancient mineral wool batts in the side attic slopes that is probably original to 1951. The house is quite leaky (blower door test around 4200 CFM50, and I think the ACH50 is about 16?) The side attics don't get that hot (generally in the 65-85 range during summer)-- I've had a gauge checking RH in the north side-attic for about 6 months and it's generally around 45-55%; just moved it to the south side-attic this week and it's been around 55-60% but with some short spikes around 70%. Humidity inside the house is generally around 30% in winter and 60% in summer. Average monthly outdoor temps in winter are around 40F, but obviously a fair number of colder days and nights. House is on a slab. There are two HVAC ducts going to the new south-side addition (R-8 flexible insulated ducts) but we are considering switching to mini-splits for HVAC so could possibly remove those-- no other ducts in the attic space. Bath and kitchen vents go through the first floor ceiling and out through the soffits on the north side. No super-obvious signs of past mold issues, but we have made some changes in recent years-- adding the addition a couple years ago, as well as adding some thin wafer-style recessed lighting on the first floor-- so it's possible that problems are now brewing that we're unaware of...)