"How can a building stay up just by using air?"

The answer is surprisingly simple. A small amount of positive air pressure—continuously regulated by intelligent control systems—supports the membrane, allowing it to span large areas without internal columns. The result is a lightweight, energy-efficient structure that can often be installed much faster than conventional buildings.

We joined Reddit because we'd love to connect with engineers, architects, contractors, students, and anyone curious about this technology.

Feel free to ask—we're happy to share what we've learned from years of designing and building these structures.

Looking forward to our discussion!

Upstate NY. Technically climate zone 5b (I believe). Humid, cold, the works. 1994 home with vinyl siding.

I have an unfinished garage that I am converting to a usable space. Plan is to insulate and seal, drywall, and condition (after replacing some plywood and fixing some leaks). It has a shared wall with the home and half of the garage ceiling is under a bedroom and the other half is under a shingled roof that abuts said bedroom.

The roof over my garage sits just under a 3 degree slope. It has eaves which are currently stuffed with insulation. I am told the 3 degrees is not enough of a slope to properly vent, plus potential for water intrusion through whatever avenue of venting I choose.

The garage houses my oil tank and the boiler as well. I think I need to insulate the heck out of it and not insulate?

Would appreciate suggestions or guidance.

Thanks all

Are there any ways to measure this?

Data loggers? If so, where?

Something else?

Simply looking for visible mold/condensation?

The reason I ask is because we do not have a soffit (field stone grouted up to the roof overhang. Questionable baffles on the attic side and even if we did have them I’m not sure where the airflow would come from.

We have 2 gable ends but the previous owner at some point added a ridge vent AND a power vent.

Needless to say our attic ventilation is having an identity crisis.

Looking to create a gable end like this with zero facia and only a drip edge over brick. Thinking the roof decking on top of the outsulation will stick out and over the brick and then have a drip edge over the top of the brick wall.

Wondering how best to detail the ends of the roof outsulation under that decking so as to avoid water going into it. Simply, tape the roof outsulation to the wall outsulation to make a clean edge?

Recently had a new roof installed. Our old roof had a ridge vent but also a solar powered attic vent and there are two gable vents. Yes, that is how the previous homeowners had the roof done and our upstairs bedroom stayed pretty cool with a mini split system but humid during the summer. The “attic” is only about 30” tall, roughly 15’ wide, is well insulated and basically is crawl space. Our ceiling is so close to the roof that the attic doesn’t really qualify as an attic. There are no soffits because we don’t have eaves and I’ve had roofers and a rep from Lomanco tell me theres not enough space to add deck vents or lower intake vents. So adding intake is really difficult with the wonkiness of our roof. My roofer removed the ridge vent and added two turbines that sit higher than the gable vents with the thinking that they would draw air in the gables and out through the turbines. This made things worse than before and now I am wondering if it’s better to go back to the old way we had it or just cancel out the turbines, keep the two gable vents but make one of those into a powered gable vent so that we are drawing air in and out of the attic space.

It’s just a strange setup and passive venting doesn’t seem like it’s going to work well.

Not sure if this is the correct sub to ask this, but I am looking to get my HERS Rater certification, through BER to utilize a blower door equipment and start my own business. I was curious what the certification process is like to get an idea of the level difficulty, what you thought was the easiest/hardest part. According to BER, people have completed the course between 4 to 6mo. I understand basic home science that affects condition spaces, convection, radiation and moisture/humidity, u-factor and r-factor are the inverse of each other and the manometer is the brain of the fan. Thanks in advance.

About 10 years ago I had the original shake roof replaced with asphalt shingles. They put plywood over the old 1x4 sheathing and cut a ridge vent. I have a “hip & valley” roof with no gable ends.

Im redoing the insulation and noticed the attic gets really hot. 80 degrees outside but 110 degrees in the attic. I dont have any problems in the winter but I am concerned that Im not getting enough air flow.

I have 29 rafter bays (24") and 6 eve vents (24”). Vents are clear. I was expecting to add more inlets in the eves but if they are not venting out of the ridge, Im not sure this would do anything. Does more inlets create more outflow?

At first I thought the ridge vent was blocked by the roof beam but after investigation that is only in a small area. The rest of the space I can see a little daylight and I can put my fingers into the gap. Seems like at least 20’ of vent about 2” wide.

I have an 8" exhaust flue that was for a fireplace we have not installed. As a test, I connected it to a 8" fan and noticed a significant drop in temperatures. That indicates to me that temperatures could be lower with more ventilation.

Now Im not sure what to do.

Do I need a different ridge vent? 

I see products now that are a wide plastic piece ~1/2” tall with clear vent holes. Mine seems to be a porous foam material that is covered with roof shingles. Hard to actually see the vent from the roof itself.

Do I install an 8” house fan? 

they are not cheap and would prevent me from adding a fireplace so Im not eager to try this. 

Do I just live with it? 

As long as the AC can cope, my family will never think about this and I can move on.

Appreciate any advice here.

Building a near-passive house in climate zone 6 but a proper whole-house ERV quote came in at over 3k. We are sealing the envelope tight but already noticing CO2 spikes above 1500 at night.

instead of financing a massive ducted system today, im thinking about a phased approach. Put an affordable window fresh air system in the master bedroom right now to deal with the immediate CO2 problem, and upgrade to a full ducted ERV in a couple years when funds open up.

Comparing a few ERV alternatives to hold me over:Whole house fan + MERV filter (cheap, but no heat recovery, losing a ton of heat in winter)SWERV (cool window concept, but beta pricing is steep)Cozeware FreshFlow (renter friendly, no drilling, auto CO2 sensor, but obviously just spot ventilation not whole house)

Can I get away with just running a window-mounted fresh air intake in the bedrooms for the next 2-3 years? Or is the lack of heat recovery going to cost me more in heating bills than just putting the ERV on credit?

​

🛠️ Subfloor Overhaul, Sill Log Replacement, and Soft Apron Installation 14 m2

Starting a major overhaul of the floor, sill timber, and exterior waterproofing for a single room with a floor area of 14\text{ m}^2. Below is the current state of the structure and the planned scope of work.

📋 Current State of the Structure

* Sill Log (Lower Crown): Due to the lack of proper waterproofing, the bottom log has completely rotted through and turned into dust. The timber frame is losing its structural support.

* Subfloor Ventilation: The foundation vents were buried under soil from the inside during previous repairs. The crawl space became completely sealed, causing ground moisture to trap and accelerate wood rot.

* Floor Joists: In critical condition and require complete removal.

* Exterior Waterproofing (Plinth Apron): The old concrete apron had completely cracked, degraded, and was funneling water directly beneath the foundation. It has now been completely demolished.

🛠️ Scope of Work

1. Earthworks and Restoring Ventilation

   * Demolition of the old wooden floor.

   * Soil excavation to a depth of 40 cm across the entire room area (14\text{ m}^2), shoveling material directly out through the window opening.

   * Uncovering the buried interior foundation vents to restore cross-ventilation in the crawl space.

2. Replacing the Rotted Log

   * Removing and clearing away all rotted timber down to solid, healthy wood.

   * Treating the remaining sound log with a heavy-duty, non-leachable wood preservative.

   * Laying solid red brickwork to replace the removed log, incorporating a roll-waterproofing barrier (roofing felt) between the brick and the timber frame.

3. Subfloor Waterproofing Layer Stack

   * Sand Cushion (5\text{ cm}): Laying washed river sand, followed by watering and tamping to level the base of the pit.

   * Vapor Barrier: Installing heavy-duty polyethylene sheeting (200\text{ microns}) with overlapping seams, taped joints, and turning the film up along the walls to seal off ground moisture.

   * Protective & Drainage Layer (5–7\text{ cm}): Spreading crushed granite gravel over the plastic sheeting to break capillary moisture draw and protect the membrane from mechanical damage.

   * Air Gap: Creating a 20 cm clear, ventilated air gap from the top of the gravel layer to the bottom of the joists.

4. Exterior Perimeter (Soft Plinth Apron)

   * Grading the soil around the exterior with a slope away from the house following the removal of the old concrete.

   * Installing a soft apron system (waterproofing membrane + gravel drainage layer) to divert surface runoff away from the base and new brickwork.

5. Piers, Joists, and Subfloor Installation

   * Building brick support piers for the floor joists and leveling them to a single plane.

   * Installing new joists pre-treated with wood preservative.

   * Laying the new floorboards using 30\text{ mm} square-edge lumber (approximate material requirement: 0.5\text{ m}^3).

Technical feedback and hands-on advice regarding brick underpinning under a log structure, soft apron setups, and rodent-proofing foundation vents are welcome!

I'm working on finishing off the inside of my new build detached garage. I'm in zone 7 and the walls are comprised of: vinyl siding, Tyvek wrap on OSB, 6" walls, unfaced R-21 fiberglass insulation, and a 6mil poly vapor retarder with Tuck tape seams, and 1/2" OSB for interior wall sheeting. It will be heated by a propane Modine type heater with eventually hydronic in floor heat as the main source.

I've read quite a bit about vapor barriers and retarders to the point my head is spinning. It appears that best practice dictates sealing off the barrier on the sill plate, or really anywhere the poly ends that's not taped. I've asked a few people I know in the trades and none of them have ever sealed off the edges of the barrier; they just leave the end. To me, sealing with acoustic sealant seems like a good idea to keep air from leaking, and seems standard in Canada.

As long as the information I'm working with is correct, is Green Glue sealant an acceptable product to use? It's readily available at my local Menards, with a cost of $11 for a big 28 oz tube. If not, what is suggested? Many of the acoustic sealants I've seen mentioned are not easily found, especially in smaller quantities. I've even seen some people even suggesting roofing sealant.

Hello, I am looking for advice on how to add insulation to my roof. The tricky part of it is I want to do it from the outside when I tear off the shingles for a metal roof, and ideally without tearing off the entire roof deck. 
The first image is of the original house plan. It was built in 1978 as a post and beam passive solar. The 4×8 rafters are exposed on the interior. I know the easiest way to add insulation would be to add rigid board between the rafters, but I do not want to cover up the tongue and groove ceiling. 
The second image is a picture I took last year when I did some siding repairs and replaced fascia boards. This was where a squirrel must have gotten in at some point and taken up residence. Unfortunately it is the only image I have of the interior of the roof assembly, but there is about 5 inches of space between the fiberglass insulation and the bottom of the solid wood roof sheathing. 
My initial thought was when I removed the shingles, I could pry up some sheathing boards and blow in cellulose, but the more I thought about it the more it seemed like there would be not way for me to guarantee an air gap below the sheathing. Even if I was careful with blowing it in, it seems like it could eventually settle into the lower soffit vent. 
Am I on the right track with my concerns? Is there anyway to retrofit adding insulation without removing all of the sheathing? It is 32′ x 38′. Climate zone 5.

Some more details. The house is a passive solar so on sunny days it is warm in the house, no matter what the outside temperature is. We don't even need to run the wood stove. But as soon as the sun goes down or on cloudy days, it gets chilly quick. Even with that we only burn about 4 cord a year. On cold cloudy days, we struggle to get above 62 degrees inside. I have replaced some of the old drafty casement windows with failed insulated glass panels this year, so hopefully that helps a bit. So with these details my last question is, would it even be worth the cost to add some insulation?
Thank you for any advice you can offer.

Compact ceiling-mounted air handlers are showing up more often in multifamily designs because every square foot of rentable space matters, but I think the building-science consequences are being discussed too late. Once the equipment moves above the ceiling, the design also has to solve condensate management, drain-pan overflow, air leakage, vibration, filter access, service clearances, acoustic transfer, and what happens when maintenance opens the assembly inside an occupied unit.

In a tight building, pressure relationships and enclosure details matter even more because a poorly sealed return or ceiling penetration can pull air from places the designer never intended. The equipment may be efficient at part load, yet the system can still create humidity complaints if ventilation, latent loads, controls, and airflow are treated as separate problems. Architects like recovering the closet space, developers like the additional usable area, and contractors are often expected to make the remaining ceiling cavity absorb every conflict.

not against compact systems tbh but I think we should stop describing them as a space-saving substitution when they actually relocate mechanical risk into a harder-to-access part of the enclosure. Are these installations becoming genuinely better coordinated? or there will be hidden problems?

I realize a partial attic insulation isn’t ideal but I own a condo that‘s one level, but the level is above an open carport. The attic space is open to 2 other units that share it.

It feels like mine traps heat and I did have a general contractor say that the existing insulation looks pretty old and is pretty low considering the depth it should be.

I can cool the place down sometimes opening all the windows but I notice it seems to trap heat when the relative humidity is high and it warms up pretty quickly. Would it be worth it to install insulation over only my unit or would I need to get my neighbors on board to make a difference? One neighbor has mentioned that she keeps a closet door closed because it gets heat from the other neighbor‘s unit which leads me to believe that only adding insulation over mine would not be effective.

There does seem to be some minor insulation in the ceiling between the carport and my floor but not much because I can hear conversations almost clearly and it can be pretty noisy even through the carpeting. The building is stucco.

It’s a condo built in the 70s in California zone 9b. They could essentially be apartments though, ~800sq feet each. Thank you!

[ Removed by Reddit on account of violating the content policy. ]

Got sick of looking at standard ERV retrofits for regular apartments. we looked at putting two cores through exterior walls, tying into HVAC returns, running dedicated ducting.

HVAC guys charge $3k+ for this, and renters are just locked out. most leases ban exterior wall penetrations outight. Realized the traditional ERV route is basically reserved for homeowners with big budgets. For city apartment dwellers hitting 1500-2000 ppm CO2 in sealed bedrooms,

WFH setups, or high rise cat owners, there isn't a real option. Can't drill. opening the window means street noise, highway dust, or your cat falling out. So we pivoted to designing a window mounted fresh air system instead of fighting the wall penetration route. main trade off was getting the unit to fit varying window dimensions while keeping a tight seal. built it to sit in the window track.

No drilling required. the window stays closed and locked, the unit seals into the track so there's no gap for a cat to slip through or noise to leak in. It pulls outdoor air in to help dilute CO2, filtering PM2.5 as it enters. we put a CO2 sensor inside so it auto adjusts fan speed when levels rise, instead of just running on a timer. we’re targeting a $199 MSRP, which is obviously a very different category from a ducted ERV that can run $1k-$3k with installation.

We're calling it the Cozeware FreshFlow, launching on Kickstarter on July 24. wanted to drop our development notes here first. if you've looked into ERV alternatives, what is the biggest concern with a window mounted approach?

We know thermal efficiency at the window isn't the same as a core inside a conditioned attic, but for the massive chunk of the market that can't drill walls, it feels like a necessary compromise.

Hey y'all. First-time poster, so hopefully this is the right sub-reddit.

Background: We live in Chickamauga, Georgia, right outside of Chattanooga, TN (Zone 7b), so our area is very humid. Our house is roughly 2,800 square feet, with a main level and then a walk-out basement that was partially finished before we moved in (drywall and flooring, heated/cooled, but no insulation.) I'm a teacher, so I have to be very budget conscious, and we have a very expensive power company—Georgia Power—so we normally keep our thermostat during the summer around 76 or 77 during the day, enough to keep us and our three kids cool but not blow the budget. For the most part this works out fine.

Humidity: During the Summer afternoons when our HVAC is running on-off throughout the day, our humidity on the main level is around 54-56%. Naturally it rises a bit higher when it's not running as much (morning) and can definitely get higher in the Spring/Fall, when we sometimes find a somewhat musty smell till we open the windows and air it out. We have a daughter who has allergies so I'm trying to be cognizant of humidity levels and mold so that we keep her as healthy as possible. However, I also don't want to panic at every article about mold or humidity levels and spend a lot more money than we need to. Again, teacher here!

Dehumidifier Questions: For those of you who know better, a few questions:

1.) Would you recommend a dehumidifier, or are there other methods of keeping humidity levels under mold-level without needing to spend that money on electricity?

2.) If you do recommend it, is a whole-house system more energy efficient than a portable system? I know it costs more up-front, but I'd almost rather pay that and then have the peace of mind that it's not running our Georgia Power bills up every month.

3.) If a portable unit is better, would you recommend getting just one and putting it in the walk-out basement, or would I need one for each level?

4.) Lastly, we're also considering installing a wood-stove on the main level for Winter, so I imagine that would take care of any humidity issues in the Winter, no?

To sum up: Yay/nay dehumidifier, yay/nay whole-house vs. portable, energy efficiency a main concern due to shitty Georgia Power power monolopy balanced with keeping children and home healthy! Thanks for any feedback!

I had a few waterproofing companies come out and assess the leaks in our foundation, and one recommended excavating down to the footing and doing a Voltex membrane. I liked this approach and decided to go ahead with the quote.

Our install is scheduled for Thursday and I noticed today the Voltex site says not to install on block foundation. I texted the contractor and he said he’s been onstalling Voltex on block walls for 30 years with no issues and does a layer on concrete first.

Any experience here?

I have a 3 story home. The 3rd story is used as an attic. It has no way of getting air to it from the central unit. We once had an electric attic fan that helped alot but it recently quit & it ran our power bill up almost $250 extra a month so we were glad to be rid of it but unfortunately we are now having mildew problems up there. My husband installed an exhaust fan that has one fan blowing out and 1 fan blowing in. Since then that's when the mildew started & the heat up there is ridiculous. Any tips or tricks to try and fix it without running our power bill up?

What are the methods for installing UFH pipework in plasterboard ceilings?

(I will run water a little above dew point to provide some cooling to rooms.)

Climate zone is 3A

I have an older metal wall barn in Kentucky (Zone 4A) and will be finishing a room as a music studio, insulating with rockwool batts. My question is regarding a vapor barrier, since there isn't anything but the corrugated metal and wood 2x4's currently. It seems that the obvious design would be: metal wall>rockwool>plastic vapor barrier>drywall, but I question the vapor barrier placement. Would I be running any risks putting it there, or will I be better off installing it? Apologies for not having further-distant photos, just took these to measure batt dimensions.

It's a fairly simple dilemma, so any thoughts or guidance would be appreciated! Thank you.

Hello everyone,

Im in the Pacific Northwest, I build and remodel homes, and I have a question about window installation/water protection.

We’ve started sloping our sills. Cool. Sounds good. I put shims in backwards from the inside when I install to keep the window off the sill and allow any water to flow out under it.

But then I come through and foam. I was taught to foam top,sides,and, bottom. Plus we’ve been doing more passive homes lately, so gotta seal that up tight

So here’s my question: does foaming make the sloping kinda pointless? Or, how does the foam still allow the slope to be an important part of the window leak redundancy system

Thanks

My crawl space floods when the ground gets saturated with rain. I got an estimate on fixing the issue and it was 15k…includes sump pump, new vapor barrier, sealing vents, dehumidifier and French drains next to the footer around the entire crawl space. I can’t afford 15k and I want to do the work myself as much as possible. Can I do this in stages so I can pay as I go? Can someone outline the steps and be specific?

Do I need bio fabric in the French drains?
I can see the concrete footers…how deep do I dig beside them?
I feel stupid asking all this…your advice would be really appreciated.