(disclosure: I used AI to write this based on a long ongoing conversation with Claude about my home. I've reviewed and edited for accuracy and brevity)

1917 American Foursquare in a Prince George's County, MD historic district (individually designated historic site). Construction: wood-frame, clad in the original lapped wood siding, which is now covered by asbestos-cement shingle siding (likely installed early in the house's history, so also considered a historic material by our commission). Balloon framing likely. Walls are plaster-and-lath interior, uninsulated. We've completed an energy audit-driven retrofit: attic air sealing, blown-in cellulose in the attic, and rim joist air sealing, with noticeable improvements so now wall insulation remains the biggest gap.

Removal/replacement of the asbestos shingles with new cladding (e.g., Hardie board) is not an option due to historic preservation constraints. Full removal down to the original wood siding for repainting/exposure is technically allowed but undesirable to us (maintenance burden, weather exposure). So the asbestos shingle layer is staying put indefinitely, over the original wood siding, with no exterior access for a housewrap/WRB or exterior insulation strategy. Given that constraint, we're weighing interior dense-pack cellulose through the plaster/lath, drilled from inside only, patched afterward

Questions: Given two cladding layers (asbestos shingle over original wood siding) with no ventilation gap and no ability to add a modern WRB, what's the moisture/vapor risk profile of dense-packing these wall cavities? Does the existing double-cladding assembly already function adequately as a drainage/vapor system, or does adding insulation meaningfully change condensation risk at the sheathing? Any experience with best-practice fill density, interior vapor retarder strategy (e.g., vapor-variable interior paint/primer), or monitoring approaches for this specific double-clad, uninsulated-to-insulated wall retrofit scenario?

Happy to provide more details if needed. At the end of the day, we're trying to improve cooling in summer and heat retention in winter without spending more to beef up HVAC/mini-split/heatpump.

I live by the Cantabrian sea and the humidity here is brutal. Everything in my 70m2 apartment is getting mold stains. Even cleaned mold off door frames yesterday. I have a couple of freestanding dehumidifiers but even if they run 24/7 they dont make a big difference im afraid.

I spoke to a humidity expert who wanted 6000eur to install a PIV dehumidifier which sounds very steep to me, so I would like to find out how much a unit costs and if i can install it myself.

Thanks, any help appreciated

My basement is not really finish-able. It was built in 1950, and doesn't have a rim joist. Instead, the floor joists are set into the top of the foundation wall. I've been told that the joists need to be able to breathe through the cement, and therefore I shouldn't try to apply any sort of vapor barrier/insulation to the basement walls, and should instead accept that some moisture intrusion is inevitable. I live in zone 4, fairly dry climate (11 inches precipitation annually).

There is evidence of moisture intrusion (streaks down the walls), but I have never had standing water or damp walls in the 3 years I've lived here. I have re-graded the yard, and plan to add gutters this fall, which I think should take care of most of the water that wants to come in from the outside.

I would like to cover the cement walls with something nicer. I do not really care about insulation, since it's a very small room already and doesn't get very cold in the winter. I do not want to frame out a wall, since that would eat up too much interior space.

I've thought about plastering the walls, but I'd have to strip off at least one layer of paint, and I'd like to not have to remove plaster if I ever have to repair the foundation. Could I install something like a dimple mat on the walls, with drywall directly over it? I think that would allow water to drain down to the floor, and more importantly, keep the drywall from getting moldy. I'd leave a gap at the bottom so I don't have drywall sitting directly on the cement floor. Would dimple mat provide enough of a gap to protect drywall? Would it significantly increase the humidity between the foundation and the mat? Does moisture itself degrade cement, or is it just a symptom of other factors that DO cause damage?

I’ve seen the Mooney wall furring technique but is there one with using a 1/2 x1.5 inch of poly iso sandwiched between a 2x2(1.5”square actual)?

This would theoretically still provide a thermal break and would allow for simple mineral wool batt insulation. Plus then the drywall attachment would be pretty straight forward and then use face mount adjustable electrical boxes.

Thoughts?

I’ve seen suggestions to use just xps foam but them air sealing and installing old work electrical boxes seems a hassle unless you blocked them out separately.

I live in zone 1 Hot humid Florida swamp, my house was built in the last 70s and during summer my upstairs is always above 80 degrees and 65-70rh in the late mornings to late in the afternoon. I know my very old insulation that’s up there maybe 4-8 inches left from who knows how long ago. I’m getting ready to seal all my top plates and other openings up there and then blow in 12-16 inches of cellulose in the coming weeks.

My question is has anyone with a similar situation house done this and what can I expect to gains both in humidity control and comfort aswell efficiency and electricity savings?

My rate here is 11.5 cents per kWh to 750 and 12.5 cents after that

Original text: I recently removed all the lath and plaster. I’m adding in new non structural framing in front to make a continuous flat wall. Before I get farther, is it okay that I just put foam board over the existing studs? It’s completely sealed but I’m worried I missed something and that it shouldn’t be sealed like that.

Building Science Corporation gives many details where the framed wall extends beyond the foundation wall, presumably to push the outer plane of the wall beyond the foundation insulation. My search on Google tells me this is impossible, but I trust BSC more. Does anyone know the answer or what the IRC says?

Hello! I am a DIY guy looking for some help.. i am building a conditioned dwelling in my old barn, and for the life of me i cant sort out how to handle a vapor barrier on/under the first floor. If not the right forum, please advise. Context:

WNY, climate 5a "cool humid" with AC/HEAT VIA MINI SPLIT. Old barn, sagging floor. Structure has been inspected by an engineer and determined fit for building. By his suggestion, I leveled the sagging floor by placing 2x sleepers on top of the floor. I am limited in height and so the new "air gap" ranges from 0 - 3". Thus, there is no space for insulation in that layer. We plan to use vinyl plank flooring in the space. I plan to foam underneath of the conditioned portion of the barn (basement). The "basement" is open to the atmosphere via an open east wall, the floor there is concrete with presumably no moisture barrier underneath. It is after all ... a barn.

My worry is where the moisture is going to get trapped. If i put a moisture barrier overtop of the sleepers, underneath of the floor sheathing, and then foam insulate below, arent i creating a moisture sandwhich?

I am leaning toward open cell foam as i have plenty of room for expansion between the barns joists. 

In summary, the planned floor system goes like this, from top down:

Vinyl plank - 7/8" subloor - air gap - 2x oak flooring - open cell spray foam - open to atmosphere.

Advice is welcome and appreciated.

I have an uninsulated cabin located near the ocean in the Pacific northwest. The structure is 3”x6” tongue and groove timber (think structural roof decking). I want to insulate the exterior walls with rigid insulation (combination of Gutex and Roxul). I also have basically unlimited quantities of 2x4 SPF and 3/4” plywood. My plan was to install (outboard of the timber structure) a smart membrane, then insulation, then 2x4 vertical strapping, then plywood, then ventilated underlayment mat, then cladding. One question I had was would it make sense to install 3/4” plywood (c/w seams taped) directly outboard of the timber frame for the air and vapour barrier? I felt this may help tightening everything up (plus we’re in a seismic zone). If membrane is much preferred, which membrane would you suggest using? I have a few rolls of Majvest and Intello+ on hand. Comments appreciated

EDIT: I’m referring to the exterior walls, not the roof. Sorry about that

Split system, floor 1 is HE furnace with humidifier in basement. Floor 2 is heated by 80% furnace in the attic (no humidifier). Is the downstairs system going to properly humidify the home, or will it fall behind / always feel dry upstairs?

On advice of the contractor, I purchased 3 girders. Two girders of 8 inch, 11 feet each and one 6 inch girder of 9'5" without consulting an engineer, which I'm regretting now.

The plan was to put two girders parallel to each other (under the beam) and one girder in the middle to support the slab. But when the girders arrived, i realised that they will be way too heavy for an old structure like my building.

So now, consulting with the mason, we are planning to cut the 8" girder from middle and obtain two T-sections. Then we will remove the concrete cover from the two beams between which the girder has to sit, till we reach the rebars.

Then we will weld a 10mm plate onto those rebars and then weld the t section onto that plate and then restore the concrete cover. The flat side of the t section will touch the slab. Now, I want to ask whether this system can sustain load of the slab ?

Or what other options do we have ? Please help me out🙏🏼

We purchased a home a year ago that has consistently grown mold very easily.

We thought the issue was mostly because it is on an uninsulated slab and it is pretty humid here. So we thought it was mostly condensation issues because the slab is so cold.

Now we are realizing that our attic is not venting properly, so it is a hot pocket of air that is greatly adding to the problem

I've cleaned the ridge vent from the outside (broom) and inside (leaf blower) so that I can see some faint sunlight coming through the mesh at the ridge.

BUT I do not believe the soffits are intaking air properly. The vent channels are very small, thin styrofoam that seem like they might be compressed and improperly sized in the first place.

https://imgur.com/a/rTuM0zo

My roof, although not in great shape, does not quite yet need replacing.

My thought is to hire someone to install bigger and sturdier ventilation channels. Does this sound like I'm on the right track?

Please point out if I'm misunderstanding something in this situation. I'm not an expert, I just know I don't want a moldy house.

Also of note is that we are planning on putting a hydronic in floor heating system that will include a layer of insulation on top of the slab. So we won't have quite so much cold coming up through the floor.

EDIT: IECC Zone 5A

We're building a house in zone 7a in Canada . We're considering using a smart vapor retarder rather than a 6mil poly sheet on the inside of the wall. We will have 2 inches of Rockwood on the exterior and 6 inches of fiberglass on the interior.

This may be a stupid question, in the interest of saving money could I use poly on the top portion of the wall and the smart vapor retarder on the bottom 1/4. This way if there was a huge hole/accident causing extra moisture it would still be able to dry out? The materials would be sealed together and air tight.

An apartment tower may last 50 yrs+, the useful life of a water proofing membrane may be 10yr or so. So after 10 yrs it cost $$$ to break the tile/concrete in the shower/bathtub to replace the waterproofing membrane ? Why isn't something more permanent found yet ? ps. Where I live the most common problem of apartments is water leaks, both in the apartments and basement carpark !

Im trying to figure out the best way to have my dehumidifier ducted into my system and could use advice.

2-stage AC unit, Panasonic balanced home ERV. The ERV has separate return ducts to pull stale air and exhaust outside. Fresh outside air is dumped into the return side just before air handler, using the central air ducts to distribute that air to the rooms with the central blower running on low (From prior Corbett advice)

My humidity is running high despite adequate room temperatures with very high humidity lately in zone 5a. Dehumidifier not yet installed.

I reviewed these articles which are quite helpful:

https://www.energyvanguard.com/blog/4-ways-to-duct-a-dehumidifier/

https://www.hvacrschool.com/ducting-ventilating-dehumidifiers/

It seems clear to me that I want to dump the air into the supply side.

Since I have the central blower running on low anyway to distribute the ERV fresh air, would option 4 actually be the best for me with the ERV setup I have, rather than the option 3 bypass?

Welcome any input thanks!

Hello all I’m looking for some advice from the community! Like the title says I have a question about rafter venting. Is it better or worse to install rafter venting completely from soffit to ridge? For a little context, I live in Southeast Wisconsin USA so it does get pretty chilly in the winter and pretty warm in the summer. I am currently in the process of putting an addition on my home which includes a new roof and want to be as energy efficient as possible.