Hi everyone, we just finished cleaning up mold and mice in my mom’s split-level crawl space and kitchen. All the old insulation had to be thrown out, and now the house is freezing.

We plan to get the crawl space sealed up professionally later, after we dig up and waterproof the outside of the house. For now, we just want to insulate the rim joists (the wood edges around the ceiling of the crawl space) to keep the cold out.

Here is what we want to do:

- No spray foam or foam boards (we want to avoid toxic fumes). We want to use something safer like Rockwool or sheep's wool.

- Seal the wood cracks with mold-free wood caulk (like DAP Dynaflex Ultra).

- Put the wool insulation in, then cover it with 6-mil plastic sealed tight with acoustic sealant and staples.

My questions:

1. Even if we seal the plastic super tight, could it trap moisture against the cold wood and cause water droplets (condensation) or new mold?

2. Should we skip the plastic and just leave the Rockwool open to breathe, or use a breathable "smart" vapor barrier instead?

3. Is it okay to insulate the rim joists now before we dig up the outside later?

Thanks for the help!

Disclosure: I'm with a building science company in the western Chicago suburbs, but this is a DIY check you can do on a cold, windy day.

1. Close all windows and exterior doors.

2. Turn on every exhaust fan you have (bath fans, range hood on high) and the clothes dryer on air-only. This slightly depressurizes the house, a poor man's blower door.

3. Light an incense stick (carefully) or hold a damp hand near likely leaks and watch for air movement:

4. - Outlets and switch plates on exterior walls

5. - Baseboards and where the floor meets the wall

6. - Attic hatch or pull-down stairs

7. - Fireplace damper

8. - Basement rim joist (where the house framing sits on the foundation)

9. - Plumbing and wiring holes under sinks

10. Write down what you find. Foam gaskets, caulk, and weatherstripping handle a lot of the small stuff.

What DIY can't do is measure total leakage or find the big hidden bypasses in the attic floor, which are often the largest. That's what a real blower door test is for, and testing again after sealing is the only way to know it worked.

⚠️ Safety before the fan test: if you have a gas water heater, furnace, or boiler that vents up a chimney, set the water heater to "Pilot" or "Vacation" and turn the thermostat down so nothing fires during the test. Don't test while a fireplace or wood stove is in use. Depressurizing the house can pull exhaust back down the chimney (backdrafting), which can bring carbon monoxide inside. Keep the test to 10 to 15 minutes, have a working CO detector nearby, and switch everything back on when you're done.
If your attic has loose, pebbly, gray-brown insulation (vermiculite), skip this test. Vermiculite may contain asbestos, and lowering the house's pressure can pull dust from the attic into your living space. Have it professionally tested first.
Other hazards worth knowing about:
**Vermiculite or old insulation in the attic.**Lowering the pressure pulls air through every ceiling gap, along with whatever dust is up there.
Fireplace ash and soot. Even with no fire going, air can come down the chimney and blow ash into the room. Close the damper or glass doors.
Crawlspace or basement air. Depressurizing pulls air up from below. That can bring in musty air, soil gases like radon, or spores from areas with microbial growth. This matters more in homes with known moisture problems.
Dry floor drains and sump pits. If the water in a floor drain has dried up, sewer gas can come in. Pouring water down unused drains first helps.
Incense or candles. It's an open flame near curtains while the house has a breeze. Use a damp hand or a lightweight tissue instead if you can.
An attached garage. If a car has run recently, exhaust can get pulled in through the garage-to-house door.

Happy to answer questions in the comments.

House walls are mostly drywall, then wall frame, then sheathing. In some spots, where there are bump outs/overhangs, the frame changes to drywall, wall frame, then a gap that is insulated on top by fiberglass, as seen in the photo. Beyond that point is what appears to be another wall frame, then house wrap, and then sheathing. Is there any reasonable way to air seal these oddly framed walls against air leakage into the attic?

Bought a house with an old garage building. Wondering if it’s worth my time/money to make it usable as an insulated workshop. Or if it’s just a teardown and use as storage for now

Climate zone 5 or 6 I think? Southern Ontario

Can see the air gaps in the siding. Thought about adding insulation batts but a wind driven rain could get them wet i’m thinking. Maybe tyvek each stud bay first, and put insulation overtop.

And yes it needs a concrete floor poured

Any advice/ideas much appreciated!

Hi all! Looking for some input on my barn project in New Hampshire. We replaced a lot of rot and lifted the barn. We are finally looking to install siding. What have you all done for a rainscreen? We are looking to install 1x12 pine vertical tongue and groove siding over a Tyvek WRB.

The difficult part is both my posts and beams are 8’ apart. I do have 1/2” CDX sheathing that is spanning those just for some extra shear strength and to keep out critters.

Any ideas would be super helpful!

Hi all,

I have a question for those who know far more about this than I do. Over the Summer, I was being billed by my electric company ( I have an electric furnace / heat system in my basement) 800,900 and 1000 from June-August.It’s likely because my home built in 1930’s has no insulation in the walls basically. I was getting quotes from an insulation company to do my living room that has the worst drafts for closed cell spray foam and when we chatted about my bills, he asked to see the attic. In the attic floor, I have the pink insulation with an r value under 30. I think he mentioned it but I don’t recall off memory.

He suggested just removing all that old junk from the floor and sealing it all up at the roof top rafters . They want to do a combo of 2 inch closed cell, and 8.5 inches of open cell in the attic. The suggestion was that would significantly reduce my energy costs. To the point where he said if it didn’t, he’d give me my money back in a joking sense. I’m doing research and I am getting super conflicting information on sealing it up. I just replaced the plywood under the roof and did new roof shingles this Summer if that matters any.

What do you guys think is the move? A point of concern is that I did the basement over ,and over the Summer I was constantly dealing with humidity and emptying tanks for dehumidifiers. I don’t want to deal with that with my attic as well, it is a pain in the neck getting up there with pull down stairs. Typically in the winter, my house as of now is cold and dry. I’m in Massachusetts if that matters any.

We are looking to insulate and seal up the unfinished basement in our 1902 home. Context: We have an exposed field stone foundation. Theres some existing fiberglass insulation, but it’s not everywhere and it is falling out of the ceiling. The faced side of the insulation is toward the ceiling of the basement. We are in central NJ so right on the edge of climate zones 4 and 5 - really humid summers, cold winters sometimes, but it’s no New England.

My plan is to first seal up the rim joist and sill plate using rigid insulation and spray foam.

I am planning to further assess the quality of the existing insulation and either replace it all or only fill in as necessary with some rockwool I have already. I want to put up a siga maijrex one-way breathable vapor barrier. For ease of install, I’d like to put it under the insulation - so it would what you see as the basement ceiling. I’m getting mixed information about vapor barriers online - especially as we’re not definitively in a super cold or super hot environment. My understanding is the siga products are newer and work differently than previous vapor barriers so I think this could be an okay approach - moisture can move through the insulation and out, but not get back in from the humid air outside the thermal barrier. (We do have a dehumidifier running constantly in the basement.)

Am I setting myself up for mold and disappointment? Would it be prudent to replace the older fiberglass insulation as well anyway so it’s all uniform - especially if I am mixing faced and unfaced insulation? Thank you!

I live in north Texas and had my aluminum framed windows replaced in March with vinyl replacement windows. The two story house (built 2005) is sided with Hardie lap siding, however all trim around the windows and corners is pine and it’s in need of replacement. The house was built with house wrap and had peel and stick membrane around all the windows.

A couple of questions for y’all before I start replacing the trim with Hardie Trim:

1. Is there any value in adding spray foam in any of the gaps around the windows?

2. Is there any value in adding peel and stick membrane to cover the gap between the frame and existing house wrap?

P.S. ideally this would have all been at the same time and I would have used new construction windows, but the timing didn’t work out.

Thanks!

Hello! I'm wondering if my crawlspace encapsulation was installed correctly - and maybe some knowledgeable folks here would know?

I recently hired a company to encapsulation my crawl space. The house was built circa 1900 and I live in a IECC Building Zone Zone 4A (Mixed-Humid) area.

They installed dimple board on the existing concrete floor and rigid foam board against the brick foundation walls, and covered with plastic vapor barrier. I noticed there are gaps between the foamboard and the foundation brick wall, approximately 1-2 inches wide, in some areas. In addition, I noticed that the foamboard terminates 6 inches below the floors. Note that there appears to be no wooden sill plate.

The company says the gaps are not an issue - but are willing to spray foam to fill the gaps. Presumably they will only fill the top of the gaps, not the entire cavity.

What does Reddit think? I am concerned about whether the insulation will perform properly and condensation risk.

See photos attached. Thank you :)

Disclosure: I work for a building science company in the western suburbs. This is general info you can check yourself, no sales pitch.

If one room is consistently colder in winter, it's usually a local insulation or air leak problem, not the whole house. Three spots to check:

1. Room over the garage. Look at the garage ceiling under that room. If it's drywalled, check for gaps where the garage wall meets the house. Floors over garages often have insulation that doesn't touch the subfloor, which lets cold air move underneath.

2. Knee walls (Cape Cods, 1½-story homes). If there's a small access door in an upstairs closet, open it with a flashlight. Look for batts that have fallen over, gaps, or open joist bays under the floor that run into the house.

3. Basement rim joist. Go to the basement and look at the wood band sitting on top of the foundation wall. If it's bare wood or has loose batts stuffed in, cold air is getting in there. On a cold day you may feel it with your hand.

Batts stuffed into gaps don't stop air. Seal the leaks first, then insulate. Happy to answer questions in the comments.

Hi! We are replacing our siding and old sheathing system. The house was built in 1978 so it had fiberboard as its house wrap... anyways we are taking it to the studs and installing 1/2 in plywood and then this system from a local James Hardie certified contractor. We are located in the Chicago land area so I'm not sure if climate zone will be a factor here- does this system seem appropriate? I'm concerned for condensation/mold growth accumulation on the ply wood, but not sure if that's just me being paranoid.

Hi all, I’ve seen different pieces of advice so I wanted to reach out to the Reddit community with a question about finishing my basement.

- Climate Zone 5A
- Block Foundation
- French drain on the interior basement wall.
- De-Humidifier running 24/7
- No active moisture coming in, but some efflorescence indicating past water intrusion. Not bad though.

I’m planning to put rigid foam boards directly on my basement block wall, tape the seams and then build the walls with batt insulation between the studs.

My question is do I really need to apply the rigid foam boards or can I get away without it? Also, if I do apply the rigid foam, should they be flush against the block foundation or leave a small gap so moisture is not trapped under it?

Thanks.

Hello all, asked my first question about insulating cathedral ceiling and received a lot of great information which has lead me down the rabbit hole of different truss styles and insulation techniques. It's a lot of info but fun to learn different techniques and building principles behind them. On to my question that I've drummed up going down these rabbit holes...

What's the feasibility of a raised heel combined with a raised lower chord truss? When talking to builders and gathering quotes, what's the best way to go about describing this? My use case is building an approx. 28x24 woodshop/gym. I was wanting to keep my wall height as low as possible while also maximizing overhead room which is why my initial thought was to go with a cathedral ceiling. However after researching insulation issues and potential costs along with reading about different truss styles, it seems the raised heel combined with at least a slightly raised lower chord could keep my insulated while gaining at least a bit of overhead room without going with 10ft walls. Any feedback would be greatly helpful, thanks in advance!

I have recessed can lights in one of my rooms that has vaulted ceilings. The lights have been converted to the screw-in LED kits with the cans still in place. The entire cavity between the sheetrock and roof deck is spray-foamed so everything seems to be air-sealed. I live in Northern Mass. (Zone 5A).

I noticed when looking at the roof outside with the thermal camera that the lights create warm spots on the roof. The light cans reduce the insulation depth by about 6-8” so I’m guessing more insulation is needed.

Should I try to remove the cans and install wafer lights with some extra insulation stuffed into the cavity where the cans used to be? This seems like it could be difficult, but doable given the cans are encased in the spray foam.

The other thought I had was to leave the cans and current LED lights and stuff some insulation in the open space of the cans behind the lights. The LED conversion kits are IC rated but I haven’t checked the cans.

Doing some research for a project and trying to understand what's typically used on green-rated buildings here. Low-E coatings in double-glazed units seem to come up most.

I read about SGG Nano, a single-silvered low-E from Saint-Gobain that combines solar control with thermal insulation, with performance aimed at green building requirements. It's offered for insulated and double-glazed units, laminated and heat-treated glass, and the shade list is long, from Icy Menthol to Blue Horizon.

What are you seeing in completed projects? Is single silver the norm, or are people moving to double or triple silver?

My basement was partially remodeled by a contractor 7 years ago & has pink insulation behind the finished drywall walls which also have tile border on the bottom. As far as I know, there is NO vapor barrier. The basement has one concrete wall and three partial walls (all three are also concrete) that are unfinished. The basement smells musty but I haven't seen mold coming through the drywall. There have been foundation cracks in the unfinished concrete walls that haven't leaked, but I just got them fixed by a professional company. There may be more foundation wall cracks behind the drywall.

1. Should I just use a dehumidifier and forget about trying to have this problem of bare pink insulation against the concrete walls fixed? I don't like the thought of just leaving the problem to get worse, since this house is one I plan to stay in long term. I'm already planning to have the rim joist air sealed anyway, so part of the drywall ceiling all around the basement will have to come down for that.

2. How do I find a remodeling contractor who knows building science and is willing to fix just the basement, and what should I plan to do about the bare concrete walls? I'm NOT doing any of the work myself, because there may be mold/mildew and I already have health problems. I'm NOT telling a random contractor or handymqn to do X Y and Z because I want to use someone who knows what they need to do to permanently fix this. The garage has had water randomly come up from the point where the floor meets the bottom of the garage wall at certain areas, but I don't know if this has happened behind the basement walls. I haven't seen it happen in the unfinished areas of the basement.

3. Since I want to get a permit with a licensed building science contractor to fix this, how do I know if the city inspectors will understand building science well enough to sign off on the contractor's plans? Is a permit needed for something like this or is it considered a repair?

4. In general, what price range should I be looking at for these fixes/improvements? The house is 1600 square feet, but the basement and garage are separated by a shared wall, so let's call the basement 1,025 square feet.

5. If you need pictures to make anything clearer, let me know what you need pictures of & I'll put them in the comments.

1986 construction, top floors are board and batten directly on studs, main floor is brick. The board and batten needs to be redone, it’s soft in areas. My contractor is suggesting to remove the bats and go over them with ZiP system followed by new LP Smart side or hardie board. They will replace any rotted sections, reflash windows, soffits and the transition between the board and boards and brick.

after some reading I found that zip system doesn’t recommend this due to moisture. I am wondering if there should be a moisture barrier between the existing board and batten and Zip system like tyvek. Or should we skip the zip system and Blueshield over the existing boards then install the new siding?

I’m not concerned about the financial aspect as I plan to live here another 20 years, I want a 30-50 year solution. The draw to the zip system is the added R value as my 2nd floor has a noticeable temperature difference.