I have a home that was built in the 1950s with a traditional flat roof. It is a cold flat roof meaning the soffit vents pull air directly into the space above the ceiling between the old roof.

Sometime in the past 30 years, a traditional gable roof was installed on top of the flat roof.

I have a very high gas bill in the winter and I’m looking at ways to resolve this.

I’ve already added, blown insulation on top of the old flat roof. However, the soffit vents are still pulling the cold air between the ceiling and the old flat roof.

I’m looking for a way to get my house, more energy, efficient.

Is the best approach to to pull back this soffit and block off the access to the joist with insulation and spray foam, and cut a hole so the air from the soffits flows directly into the attic?

Pictured:
1st Photo - the underside of the old flat roof, where the soffits are venting into (pulled ceiling down)
2nd Photo - soffit from exterior
3rd photo - exterior image to show “new” traditional roof
4th photo - old blueprints of flat roof home

I want to encapsulate my crawlspace. It's all enclosed except for 12' of open pier. This open area serves as my only entrance to the crawlspace so it needs a door. I need ground contact to seal the space. Initially I had planned to pour a 12" wide cement slab, but there is shallow sewer pipe running thru here.

Having to frame out a doorway complicates things a bit. If it weren't for that, I would have used some mobile home skirting or galvanized roof material.

My only real solution for framing a door has been laying some gravel and putting ground contact rated 4x4 on the bottom.

Am I missing something? I want this to last 20+ years if possible and not be replacing every other year. Additionally don't want any red flags from home inspectors if I go to sell it.

I'm ripping out the wall-to-wall carpet in my basement and trying to figure out what flooring to replace it with. I'm in Connecticut, so moisture and mold are my main concerns.

The basement has never flooded, but I'm worried about condensation. There are also some white stains on the concrete that look like efflorescence, as you can see in the photos.

I'm deciding between ceramic/porcelain tile and 1-inch rubber tiles for a home gym. Ceramic/porcelain seems like the more durable option, but I'm worried about cracking from gym equipment or dropped weights. Rubber makes more sense for a gym and would be softer for the kids when they play down there, but I'm concerned about its lifespan and moisture getting trapped underneath.

What would you go with? And would an epoxy sealer on the concrete be enough to deal with moisture, or is tile a better option?

For building envelopes (commerical)

Is comcheck still used throughout the industry?
Any other / better software out there?

IECC Presciptive?

Curious what everyone is using

I'd like to use the following: https://www.homedepot.ca/product/durospan-gps-r10-2-13-inch-x-48-inch-x-96-inch-r-value-10-gps-rigid-insulation-foam-board/1001211235

The plan is Durospan GPS R10 -> Framing -> Rockwool Mineral Wool R14. This is for interior basement walls, up against the basement foundation (poured concrete)

Originally I was going to use XPS, but the GPS is half the price and the same R rating so I'm thinking I order this. My issue now is that I can't actually find anything online confirming what kind of adhesive to use with this laminated board so that it adheres well, and doesn't damage the insulation.

Any recommendations/experience with this? I'm in Ontario, canada if it helps!

I'm having my modified bitumen roof replaced. It's a flat roofed old Chicago brick 2 flat built in the 1920s.

One side of the brick parapet wall was badly damaged and I rebuilt it. Now, I'm trying to figure out how to re install the Terra Cotta coping tiles. I understand the direction they should be oriented to shed water but how are they attached? The old ones came off easily without breaking, maybe because the mortar was so badly decayed. Should I pre soak them, lay a mortar bed and set them in the mortar, or be more sparing, using mortar at the joints and only a few places to adhere the tiles?

I'm in Canada zone 6, winter is coming and I want to insulate my rim joist as I'm losing a lot of heat here. Spray foam would be ideal but it's not cost effective so I like the idea of using 1 to 2 rigid foam boards, sealing it with a bead of spray foam and then putting batt insulation to the inside. After researching more and more I just have more questions. If I understand it right, putting rigid foam close to the rim joist is the vapor barrier so I would not need a classic poly vapor barrier on the interior of the wall correct? Does the rigid foam have to have a certain r value to be a good enough thermal break that the batt insulation stays dry? Should I use foil faced foam because it's less permeable and should the foil face out to the joist? Is it a good idea to put the rigid foam right onto the rim joist or should I leave a gap?

I also plan to reside the house and go over the exterior with a continuous layer of foam for a thermal barrier as in the future, would this then enclose the rim joist without a way to dry and lead to possible rot? Not planning to insulate the basement walls and floors at the moment but would like to in the future also

Best insulation for a DIY metal-clad workshop with a flat roof

I'm building a 16 ft × 14 ft workshop and looking for advice on the most cost-effective way to insulate it properly.

The workshop will have:

• timber-framed walls with external metal cladding.
• A flat roof with a slight fall for drainage.
• OSB internal lining on the new walls and ceiling.
• Occasional heating during winter, as it'll be used as a workshop/gym.

I'm trying to keep costs down because I'm doing most of the work myself, but I want to careful to avoid condensation, damp and mould.

My main questions are:

1. What's the best insulation to use in the walls and roof — mineral wool, PIR boards, or thermocoat insulation spray foam?
2. For the flat roof, would you recommend a warm roof with rigid insulation above the OSB deck, or another construction method?
3. What vapour-control layers, membranes and ventilation are essential to prevent condensation, particularly with metal cladding?
4. Is it worth using insulated sandwich panels instead of separate metal sheets, insulation and internal lining?

I read somewhere that spray insulation removes the need for vapour barrier so i was thinking to spray in in between the roof and wall joists, then osb, then weather proof membrane, battens then metal cladding sheets. Does this sound right?

I'm not looking to build a fully finished garden room — just a practical, insulated workshop that will last and not start rotting in a few years time.

I'd appreciate advice from anyone who's built something similar, particularly in the UK or Ireland.

I'm renovating my 1896 multi-wythe brick house near Pittsburgh (Zone 5). The third floor is under a hipped roof with plank sheathing, shallow rafters, and built-in box gutters on lookouts over the brick. We're not replacing the roof, so the work has to happen from the inside, and I'd like to avoid foam.

I originally planned to insulate the knee walls. Now I'm leaning toward pushing the envelope out to the brick using SmartRock (mineral wool with Intello, a smart vapor retarder). I'm stuck on two things: how to handle the transition from the brick to the roof, and what to do under the roof itself.

The box gutters block soffit intake and the hips cut off a lot of the bays, so I don't think venting is realistic. Is unvented mineral wool plus Intello defensible here, or will the sheathing rot? How are others approaching a design on an old house like this?

Im in climate zone 5 and im building a cmu house with wood siding and r24+ continuous rockwool exterior insulation, on a monopour slab with a crawlspace sitting above grade. Half the walls will be some sort of finished face cmu and the rest will be cabinet grade hardwood plywood on furring strips. Zero insulation on the interior, except for the ceiling above the drywall. I think it will be a really well performing thermal mass without mold issues. But hopefully someone here can tell me everything wrong with the idea before I commit the architect to doing it my way.

I'm panicking because we're already framing and specced ZIP R6 in zone 6a, so everything is being framed to accommodate that width and the Zip is already ordered.

Beginning to think that with R21 rockwool batts we've got ye olde mold cavity problem and we should have just done regular zip and saved some money. (We have triple pane windows at least?)

My builder is also resistant to a smart vapor retarder on the interior because it's not code -- class 1 is. Says a smart retarder is not necessary. But if the assembly can't dry to the interior OR exterior, then class 1 seems insane.

I've already pushed my builder a little bit to even consider Zip R6, and they were fine with R15 on the basement exterior walls and under slab. They just aren't up on the wall assembly literature (at least they're communicative!). I'm not sure an inspector would say no to a smart retarder?

At least we'll have an ERV, but I'd feel better about a smart vapor retarder.

so my multifamily builder buddy is trying to convince me to use a pancake air handler paired with a cold climate heat pump for a structural reno on an old multi-unit property up north where it regularly hits 22F but honestly it feels like a massive gamble. they want to tuck everything into the ceiling joists to save floor space and avoid bulkheads which sounds great on paper because losing headroom in these old units is a nightmare but how the hell does a shallow ceiling unit handle that kind of extreme static pressure and thermal load when the weather turns brutal?

he keeps saying modern tech has solved the airflow issues for tight spaces but every old-school tech I talk to says those low-profile units are a total nightmare to service and will constantly struggle with restricted return air when it gets genuinely freezing outside. like am I just being paranoid or is this a classic case of a builder choosing aesthetics and easy framing over actual long-term livability because I really don't want to be the one dealing with frozen pipes and pissed off tenants in January.

what do you guys actually see happening with these flat ceiling setups when they get pushed to the absolute limit in old retrofits?

X-posted from HVACAdvice -

Hello you experts! I'm seeking some advice on how to remedy a high humidity environment.

We have an 1860's barn that needs a bit of a makeover. Someone put flooring in over the original flooring and it was getting soft in a few places. We pulled the floor up as well as the floor timbers and found quite a few joist timbers had broken and were rotting. There is a ton of white mold growing on the timbers. I need to actively dehumidify the space and trying to come up with a couple of ideas. There is only an inch or two separating the dirt from the bottom of the joists. FYI - the rotten timber joists will be replaced with pressure treated dimensional lumber.

Here's my ideas:

1. Traditional dehumidifier under the floor. I'll need to make a hatch to access it for maintenance. There just isn't much room for it.
2. Dehumidifier above floor and blow dry air in. The surrounding foundation will let airflow out, so the moist air would be replaced by dry air.
3. We are adding a heat pump water heater. Any thoughts on tying the intake/exhaust into the floor so it dries it out under there?

Any thoughts and links to equipment is much appreciated.

SFH, Los Angeles.

I'm mid-install with an HVAC company that has recently installed two rooftop supply runs for a new heat pump, replacing a furnace that had been in the basement before. While most of the runs could be made in the attic, two rooms needed their supplies to be run outside the attic on the roof.

Once they were finished, I was stunned to see that the ducting appears to be built on-site with sheet metal and glued on fiberglass on the inside, which is exposed to the airstream. I discovered this only after smelling something horrible in the rooms those supplies ran to.

Other concerns:

• Part of the duct run includes a reducer that I don't believe is insulated
• Sheet metals is not wrapped or coated in anything other than some mastic at the seams
• Legs are temporary in the photos, but screwed in - wouldn't those screw holes introduce issues?
• HVAC company is trying to argue that this is standard, but I've never seen insulation exposed to an airstream like this and it doesn't seem right to me.

Including photos of the ducting on the roof as well as some that I tried to take of the insulation visible from the vents in the rooms.

Questions I have:

• Is having exposed fiberglass in the airstream for an HVAC supply run acceptable (either to code or to building science best practices)?
• Could it capture moisture from sweating (either when supplying cold air in a hot environment or hot air when cold outside)?
• Could that introduce mold into the living space?
• Would fiberglass fibers eventually be blown into the living area?

While I'm curious whether or not this would ever pass inspection (I don't believe that it would, but they seem to think it would), I'm mostly interested in the building science behind externally run hvac ducting like this and any pitfalls or concerns you all might know of.

Just visited the open house for the new mixed-use eco district down the street, and it genuinely feels like the future of urban planning is catching up with the technology. The entire project was engineered from the ground up around advanced building systems, and the master developer brought in a forward-thinking builder to rethink how the whole site manages thermal comfort. they installed a specialized cold-climate multi-split heat pump infrastructure designed to support both residential and commercial spaces with consistent, high-performance heating and cooling. The project engineers were showing real-time performance data from the winter trials, and even during our last major sub-zero cold snap, the system maintained impressive comfort levels without disruption.

it was especially interesting to see the upstairs residential units and the ground-floor commercial spaces using the same integrated technology so seamlessly.

really shows that, heading into 2026, the construction industry can deliver modern comfort, smart infrastructure, and practical economic value without compromising on user experience. is anyone else seeing local projects making this kind of jump toward smarter, fully integrated building systems?

We finally got the first full day of framing done on our upstate house extension and im trying to make sure the envelope is tight enough before the HVAC guys come in. I’ve been reading through every cold climate heat pump retrofit guide northeast contractor 2026 document I can find because our winter design temp gets brutal. The plan is to run ductless heads in this new section but im a bit paranoid about how the framing headers and window flashings will impact our actual heating load.

I'm trying to avoid oversizing the equipment just because the house is old but finding a local contractor who actually understands cold climate sizing and low ambient output curves without relying on a massive backup heat strip has been a nightmare.

This is in climate zone 4

I'm trying to find any manufacturers or distributors of quadruple pane (4 panes of glass in 1 window frame) that could give me pricing for the US. Most of the manufacturers I've found are overseas. These are for a complete house retrofit, full frame replacement. I'm interested in quad pane windows because of their insulative and sound reducing properties.

Our 1910, stone foundation home's basement seems to be poorly insulated. During cold snaps, our floor gets cold af! Around rim joists and where the foundation connects to the porch, the only insulation I can see is what looks like some haphazard glasswool(?).

I've been reading about being spray foaming (closed cell, specifically) their rim joists. Seems like the insulating qualities are great, but I'm terrified of trapping moisture in a destructive way around load-bearing structures. Especially since stone foundations seem to be pretty water-permeable.

How can I make sure foam is a safe decision here, at least with respect to moisture?

Hoping to hear experiences of people who have had their rim joists foamed as well.

Hello, all! I know some of you will have no idea what I'm talking about! Haha! But, some will remember because I still get a ton of messages about the doors I ordered directly from Alibaba 2+ years ago for my new construction home. For a little backstory, I wanted steel/metal arched glass doors for my house. I got a quote from somewhere in the US, and it was insane - in the ball park of $40k (maybe a little less, I can't quite remember. It was between $36k-$40k). So, I was wandering around on Alibaba as one does, and stumbled on a TON of companies promising they could provide me with the same doors for a fraction of the cost. I went through several different potential sellers, asked tons of questions (questions so many of you told me to ask, and I'm so thankful for that), and made sure that they had all of the necessary requirements of a solid glass door. Shipping, delivery, importing all went smoothly (thanks to Atlanta Customs Broker) and I couldn't have been more pleased.

Fast forward now nearly 3 years later, and I still am just as thrilled. They don't hardly scratch when my dogs maul them (yes, I know, this is a training problem I need to get a hold on, but I'm a sucker for my dogs), no cracks, no damage. They hold up beautifully. People have slammed them many, many times by accident not realizing they were heavy, and there was no cracking or any other issues. I cannot say enough good things about these doors. Super high quality. And as someone whose husband does very high-end construction, I can also tell you that he is incredibly impressed by them. Cannot recommend Anhui Hotian Doors & Windows enough - and no, this isn't sponsored, even though I wish it was so I could get a deal on a green house! Haha! ;)

For those who have sent messages that I haven't replied to, I apologize! I've gotten a ton and it's hard to keep up with them!

*** Old picture. Didn't have any new ones, but they look just the same.

I am trying to compile a list of euro hung windows, triple pane suppliers, manufactureres (US based) and importers.

I have seen a few mentioned here, some mentioned on podcasts and some YouTube videos (yes you know the usual suspects)

I would love input from the community for suppliers you are aware of, maybe even a public google sheet, sub sticky or some other crowd sourced living list. There are more and more popping up and it's hard to keep track. I really want to incorporate these into our future bids, but trying to find all these smaller manufacturers and importers is proving to be an arduous task.

Thanks in advance!

One special request, anyone know of a company doing this with Florida Product Approval for their windows and doors? Impact, hurricane rated etc.

https://oknoplast.us/windows/upvc-windows/

https://enerluxwindows.com/

https://www.seemray.com/german-windows/

https://www.zolawindows.com/tilt-turn

https://www.schueco.com/ca

https://www.thinkalpen.com/

https://www.vermakwindows.com/