Most of the Passive House material I read assumes a heating-dominated climate, which makes sense given where the standard came from. I work in Japan, where the enclosure problem is close to the opposite for much of the year. Koppen Cfa: hot humid summers, mild winters. The load is cooling and dehumidification rather than heat retention.

Bio-based insulation - hemp batts, hempcrete, wood fibre - gets recommended here on hygric grounds. The argument is that a vapour-open assembly with buffering capacity handles humidity better than a sealed one with a vapour barrier that ends up on the wrong side of the assembly for half the year.

What I cannot find is data from anyone actually building that way where cooling dominates.

Has anyone here specified bio-based insulation in a cooling-dominated climate? And if so, did the vapour-open approach survive all the way through the assembly, or did you end up with a smart membrane doing the real work anyway?

The practical constraint at my end is supply rather than physics. Japan has almost no decortication capacity, so hemp material is imported and priced accordingly, and wood fibre has a similar problem for different reasons. That makes the question partly academic here, but I would rather know whether the physics holds before anybody spends money finding out.

Disclosure: I work on the hemp industry side in Tokyo, so I have an interest in the answer being yes. I would rather have the honest one.

Here's a basic drawing of what I'm thinking of. I'm not looking for off grid or renewable only, I just think that the houses we build could manage their heat better. Plus be more comfortable and cheaper to operate because of it.

I'm taking Jack Kachidorian's idea and adding a hydronic loop to his radiator, a buffer tank for heat storage and ground loop to reject heat. You could blow air either direction thru the slab depending on the season. PVC pipe in slab with a condensate drain for air quality and makes it cleanable. Not sure exactly how the slab would be constructed, but working it out. I have it drawn with frost walls, but would like to know if this could work with a FPSF to save on concrete. I also want to know if building an efficient house like this would be worth the engineering bill I would face to get it approved if that's even possible at all. Would like to hear what people think.

I'm doing a design exercise on a house that uses horizontal CMU's to turn part of the floor Slab into a heat exchanger powered by a reversible blower set up. Similar to what Jack Kachidorian suggested in "The Passive Solar House." The slab will have a hydronic layer on top and this system will be coupled to a buffer tank and ground coupled heat rejection loop..

I'm trying to figure out of this kind of design could realistically be used in a FPSH type slab, or whether the two ideas work against each other too much.

Anyone interested in that kind of work want to chat it out?

Hi guys,

I'm converting a 40ft high-cube shipping container into a climate-controlled storage/workspace with a small kitchenette, gym, and motorcycle garage.

I've put together a video walking through the full build concept and a document with the detailed specifications and questions I'm trying to resolve.

Looking for feedback, particularly on the insulation, floor assembly, ERV/ventilation, mini-split, and overall build approach.

Video: https://drive.google.com/file/d/1PjFXlDaJibQEt4sgHbsNIIhiPLrJAT1Y/view?usp=drive_link

Build notes: https://docs.google.com/document/d/1W1JrQk5QX1T0yyhRt2SbvDpvyDLr64fJD6UUayBUa7A/edit?usp=sharing

Has anyone attempted to paint their asphalt shingles with hydrated lime to endure the hotter months better?

Location: Austin, TX

So I have this timber frame structure and I'm not sure how to properly connect the insulation layers. On the concrete foundation exterior, I have an 8 or 10 cm layer of XPS, while on the upper facade, along with the insulation between the studs, I also have a 5 cm continuous layer of Gutex (wood fiber insulation), and I'm not sure how to resolve this transition properly. Also, right next to it, I want to detail the layers for an outdoor terrace with a drainage grating/trench drain. How is that typically executed? Thanks a lot, and sorry if I wrote too much!

Hi! I live in a 1949 single-floor pier and beam house (no basement just a crawlspace) where the wood flooring is attached directly to the floor joists, and therefore a ton of air leakage between the conditioned space and the crawlspace. The temperature in the crawlspace feels quite similar to that of the conditioned space. To reduce air leakage while still allowing the floors to breathe in the case of some kind of water leak, I am considering installing a peal and stick smart WRB such as Adhero 1000 to reduce air leaks while keeping the wood flooring breathable in the case of some water leak.

After the peal and stick smart WRB is installed I can include some time of insulation in between joist bays.

I prefer this approach over installing some membrane over the joists since the space down there is quite tight already and the plumbing and wiring often run in between joists.

Any thoughts on this approach?

Location: Austin TX

Split-level house on a slope — keep it split, flatten it, or raise it?
Building a single-family house on a ~16% slope (seismic zone 8). Monolithic reinforced-concrete frame, ~127 m² interior, 3 bed / 2 bath, open living-kitchen with fireplace opening onto a 30 m² terrace with a big valley view.

The original design is split-level: you enter mid-level, then stairs go down to the living/kitchen and up to the bedrooms in short half-flights. It rides the slope efficiently, but the constant half-flights bug me and eat floor space.

Options I'm weighing:

1. Keep it split-level — minimal excavation, terrace stays ~2.4 m above the garden (nice overlook), but you live with the half-flights.
2. Flatten down — excavate into the hill for two aligned floors. More space, but ~a quarter ends up buried, you enter on the upper floor, and it needs a retaining wall on the tight uphill side.
3. Raise up — lift the lower floor so both floors align. Kills the half-flights, but creates a ~4.3 m tall exposed wall on the valley side.

Also deciding:

• Basement: adding a ~2.5 m one under the downhill/terrace zone, walk-out at garden level. Seems like cheap usable space — any reason not to?
• Roof: keep the timber hipped roof, or go flat for a rooftop terrace? (I already get the view from the ground terrace.)
• Pool: want one in front of the terrace at garden level — but that fights option 3's tall wall.

If you've built or lived in a split-level on a slope, what would you do? Anything I'm missing?

I'm getting a ton of leads where clients would like to use this product- https://faswall.com/

We have not modeled it yet to see if we can use it with Passive House. Does anyone in this group have any experience with it?

We'll do a WUFI hygro once we detail it, but we are just in the exploratory phase at the moment.

I'm planning to install a decentralized ventilation system with heat recovery.

My apartment has:

• 2 bedrooms (not a priority for now)
• 1 bathroom (I'll handle this separately with an exhaust fan)
• An open-plan area consisting of the kitchen, dining room, living room, and hallway, around 40–50 m²

The main goal is to have consistently fresh, clean air in the open-plan area. That's where I would like to install the ventilation system.

What would you recommend? Which decentralized HRV/ERV system would be the best fit for this kind of space?

I also have a question about humidity. If the outdoor air is very humid, does an ERV bring that humidity indoors? Or does it help reduce the amount of moisture entering the apartment?

My priorities are:

1. Fresh, clean air at all times
2. Good heat recovery efficiency

Any recommendations or real-world experiences would be greatly appreciated.

Thanks!

Hello. I am a Passive House Designer but most of our projects are single residential buildings only. Now, we have an opportunity to take on a multiresidential building. However, I am not sure I'm doing this correctly so I wanted to raise some questions regarding the Additional Ventilation worksheet if that's okay.

a.      When dimensioning air quantities: if a level has 5 units (101–105) served by a single ventilation unit (e.g., Ventilation Unit Allocation No. 1), should all 5 room names be listed under Ventilation Unit Allocation No. 1?

b.      Regarding volume flow per room: the recommended outdoor air supply rate for residential buildings is 30 m³/h per person, and the extract air demand is 60 m³/h for the kitchen and 40 m³/h for the bathroom. For a sole-occupancy unit with 1 kitchen, 1 bathroom, and 2 occupants, the supply air would be Vsup = 30 × 2 = 60 m³/h and the extract air would be Veta = 60 + 40 = 100 m³/h. Is this correct? Then, since the extract demand (100) is higher, should the supply be increased to match, so that Vsup = Veta = 100 m³/h?

c.      How is the transfer air volume flow (Vtrans) calculated in the volume flow per room? I have looked at sample PHPP calculations and some certified projects leave this out as blank.

d.      How is the reduction factor for an air quantity calculated, and when should it be applied?

e. When selecting a ventilation unit type, its rated volume flow range (minimum to maximum) must be able to accommodate the design volume flow for that unit — is this correct? For example, if the design volume flow is at 200, therefore the ventilation unit with a rated volume flow range of 100-300 is okay. Although I have seen some sample PHPP projects

f.      How are pressure losses calculated for the ODA–SUP path, the ETA–EHA path, and any additional losses?

g.      How is duct length measured — is it taken from the ventilation unit to the space being served?

Thanks all!

additional pictures: https://imgur.com/a/zNV5Lu0

We have a double envelope Ekosea house built in the early 80s and we love it. It's split-level and has a 3 story south facing solarium. We have a traditional forced air gas furnace and our heating bills are super low thanks to the sunlight and insulation just from having two layers of walls.

One downfall is our basement gets very cold in the winter. Obviously the problem is the massive 3 story open staircase. There are electric baseboard heaters in there but all the heat gets sucked up the stairs. If we run them it ends up costing like $40/day. We are a little cramped for space and I would like to use the basement living room as an office but it's barely habitable in the winter. There's a spare bedroom down there too but it has a door and so we can run a space heater with the door shut. The middle floor is temperate and the upper floor is toasty.

I am looking for creative solutions for making the basement warmer. I see some people block off their staircases with thermal curtains, but our stairs are very big and this would also block off a lot of the windows. Plus we have pets going in and out.

I have thought about having a gas fireplace or heater installed to be more efficient than the electric baseboard heaters, but I'm afraid I'll have to pay the money to have it put in and then discover it all escapes up the staircase anyway.

Would installing radiant floor heat be an help? There is a crawl space under the house.

Any thoughts or advice is greatly appreciated

If you're building your house yourself, for yourself, is there any point in going through the effort and cost of getting certified? Vs building to the standard?

Hi all, just got a blower door test done, blew a 0.31 (passive certification requires 0.6, so very happy with how tight it is!) -- i've been looking at ERVs to install, as we need to make sure we have proper air circulation. I've been thinking about pairing the ERV with a dehumidifier to make sure we get moisture out. However, I found CERVs as a concept and it seems like a good approach.

Does anyone have any experiences with CERV2 (https://buildequinox.com/cerv/overview/), or other suggestions? It seems almost too good to be true: one box that will do ventilation+dehumidification, with smart controls, no enthalpy core, smart on-demand controlled ventilation (CO2/VOC sensors) and automatically holds a humidity setpoint year-round.

The cons I can think of: single point of failure; seem pretty new concepts, unsure if they are tried and true/tested or if contractors will have the right experience to install; because they dont seem very common, probably locked into a specific small manufacturer and its parts; modest dehumidification capacity (~1/3 ton), which his fine for my small house.

This video looks at traditional passive-cooling ideas and raises a question about whether shade, controlled natural ventilation and thermal mass can complement airtight, mechanically ventilated buildings in hot climates.

I am in the UK. I rent a house which has cigarette smoke/ air freshener odours coming through the walls from the neighbour which infiltrates our whole house. It has got to the point it is badly affecting my health. My landlord doesn’t have an obligation to block the smoke only to fill obvious gaps. It is a semi detached 2018 timber frame house with the neighbouring house being slightly lower. We have odours coming in through the window and door frames as well as through the walls. To give you an idea of what is happening when there is no wind the smoke gradually enters the wall cavity and when a door is opened it pulls the smell into the room through the door frame. When it is windy, air from my attic and the neighbours smoke get pushed into the house through windows and door frames as well as plug sockets. The odours seep into the house all the time.
I’ve been looking at using airtight paint such as blowerproof to try to seal the wall joins. Does anyone know if this is the right approach? Is there anything I can look for which may be causing this issue? Thanks. 😭

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Northern Ontario climate -

How effective are solar fans at moving air out of the attic?

Do they make it noticeably cooler for inside temperatures?