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Detailed Assemblies for an Airtight Small Home

finehomebuilding.com

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Re: Detailed Assemblies for an Airtight Small Home

#61

Post by londons_explore »

HPsquared wrote: post #57
lbotos wrote: post #10

Earlier quoted context omitted.

FTA: > It was to determine how well the HRVs How many of those homes tested installed a proper mechanical ventilation system? Anyone that is serious about air tightness will tell you that you need to manage the air transfer with an HRV or an ERV so it's filtered, controlled, and avoids these problems. --- I found the study you are quoting: https://pureadmin.qub.ac.uk/ws/portalfiles/portal/31281945/C... Results from t…

It's a risk when building homes for the general public, things like ventilation need to be idiot-proof. Maybe a big red warning if the system isn't working properly? Mandatory inspections?

The solution is sensored operations. The air system needs to measure the amount of CO2 and PM2.5 in each room and adjust automatically to maintain fresh air everywhere.

"Turned off" should be considered a dangerous state you can't leave the system in - in fact, if due to some failure the system ends up turned off, it should continuously alarm or trip the electrical supply.

Just like it's really hard to turn off the drivers airbag in a car.

Re: Detailed Assemblies for an Airtight Small Home

#62

Post by semi-extrinsic »

ramraj07 wrote: post #51
WalterBright wrote: post #43

I bought a CO2 monitor. What a shock it was to see my office go over 1000ppm. I had no idea. Now I crack the window, and tweak that till the CO2 stays below 600 or thereabouts.

Aren’t there heat exchanging ventillation systems that do this (maybe even better) without wasting a ton of energy?

We had a good one like that in our previous apartment. They consist of a large cylindrical metal "heat sink" where cold air coming in goes through the bottom half, warm air going out leaves through the top half, and the entire thing rotates at ~ 5 RPM. Not any more noisy than regular kitchen ventilation. But they need to be big, ours was the size of a small dishwasher and that was adequate for a 75 square meter apartment.

Edit: if you are buying such a thing you should get someting oversized, e.g. for a 180 square meter home you should find a unit that is specified for "200 to 350 square meters", not "75 to 200".

Re: Detailed Assemblies for an Airtight Small Home

#63

Post by bryanrasmussen »

ars wrote: post #25
wffurr wrote: post #4

Earlier quoted context omitted.

You can open the door or window.

While you are sleeping? But according to google it would take a week to die from too much CO2 in a sealed room.

hmm, now I suspect Google may be purchasing carbon offsets and piping the extra C02 into people's houses.

Re: Detailed Assemblies for an Airtight Small Home

#64

Post by robocat »

hedora wrote: post #19
synicalx wrote: post #14

Earlier quoted context omitted.

I assume, steam causing moisture build up and associated mould and rot. That's a problem easily solved with a $20 exhaust fan though.

The cost of the fan is dwarfed by labor, and you’re not getting a fan you want to live with for $20. Also, at least in California, you have to hook it to a janky humidity sensing switch that costs more than $20.

> humidity sensing

Anyone have links to working designs for humidity controlled fans or similar - preferably Raspberry Pi?

I want an indoor sensor and an outdoor sensor, and to run the fan only occasionally (maybe 10 minutes a day) and only when outdoor humidity is much lower then indoor humidity. For holiday sleepout, that sometimes gets damp, but outdoors is sometimes high humidity so no point running fan in that case!

I've looked at household ducted fans, but they don't really do what I want.

Re: Detailed Assemblies for an Airtight Small Home

#65

Post by kkfx »

jweir wrote: post #7

Air tight homes and health problems. https://www.cibsejournal.com/news/airtight-new-homes-creatin...

I've built my new home few years ago, so airtight according to local norms (France) and with proper ventilation, as computed in the project: IME the article have a small point in the sense that:

- there is much more dust in wood-frame + glass wool homes than in classic masonry ones, so while formally anything is done as it should there are still a bit too much particles of I-do-not-know-what. So far (5y) I experience no health issue though, no specific sign of even little suffering, just noticing that I've clean around the double dust than the ancient home, perhaps people who already have respiratory issue might suffer;

- even if formally calculated as it should I feel the need of a little bit more ventilation than the computed one. Air quality remain constant, so for instance in the bedroom I do not experience "morning poor air" that's a normal thing in classic houses, similarly if I hold a party perceived air quality stay essentially the same BUT when I'm outside I feel a better air, with a different significant enough to think that few m³/h would be far better.

Beside that the article probably see restored houses, so houses where changes are constrained by something preexisting and compromises became a must, where much of the work was done "on experience and cheapness basis" not on seriously computed design fueled also by customers who do not understand much the tech. IME the overall quality of new home is still superior to the classic one, far lower humidity, far more constant climate matter.

Re: Detailed Assemblies for an Airtight Small Home

#66

Post by rapjr9 »

londons_explore wrote: post #59

The main reason to make a building airtight is for energy efficiency. But it's pointless to go to such lengths for airtightness if you have massive thermal bridges in the walls and roof in so many places. If you want to be really efficient, the insulation should be constant thickness with no nails or screws poking into it, and certainly no bits of wood across it. Since the insulation has no mechanical strength, that…

Building a house within a house would also add a lot of soundproofing. I wonder if anyone has studied whether people like or dislike not being able to hear what is going on outside the house. Seems like there would be some safety issues, like you can't hear someone outside calling for help and can't hear how intense a storm is or if a car/truck drives up, but on the good side you also can't hear the neighbors lawn mower and wood chipper. Some people may like feeling connected audibly to the outside world and feel more isolated if they can't hear nature while others may like that it makes the outside world go away. It may not be possible to hear wind chimes. An emergency siren may be difficult to hear, though emergency sirens are not used much any more in the USA, except near nuclear power plants and such. Maybe that needs to change with climate change. In fact, changing climate may need to be part of the calculation on how houses are built (not just increased wind resistance but also estimates of how warm/cold the area will be year round in the future.) It would be great if houses could be 3D printed so people are not limited by increased costs due to homebuilders not upgrading their skills. House design may need to change radically on the East Coast (Nor'easters's) and in Tornado Alley and on the South coast (hurricanes).

Re: Detailed Assemblies for an Airtight Small Home

#67

Post by kkfx »

VectorLock wrote: post #6

How much does this construction cost vs. standard building? Looks like it could be relatively cost competitive.

Here (France, and my original country, Italy) costs are complicated to judge: in mere raw materials the cost is far lower for new wood frame houses, but in term of final price is significantly higher, partially because they are a relatively new concept in south/central EU and partially because most enterprise are small ones who do not work much in "modern" terms than in their own workers experience and so they need external enterprises to design and test stuff like windows design for passive heating from the Sun, how much cover windows for avoid Sun when climate is hot, how to design low-inertia heating with heat pumps, Canadian well, dimension a solar p.v./aerovoltaic/* systems etc and while those systems are technologically simple they are sold at higher prices for what they are for similar reasons.

The lack of mean awareness and expectations probably permit high prices. In cost terms what I can say is essentially: more initial capex, far reduced opex IF anything is well done. Seen inflation capex/opex ratio means reduced TCO if you buy to stay for years and years at least, resale value so far is a bit crazy for the already described reasons...

Re: Detailed Assemblies for an Airtight Small Home

#68

Post by ClumsyPilot »

Cthulhu_ wrote: post #60
ramraj07 wrote: post #51

Earlier quoted context omitted.

Aren’t there heat exchanging ventillation systems that do this (maybe even better) without wasting a ton of energy?

Yes, but they may not be effective enough; there was a big stink in the area I live where they had houses with a system like that, but the system either didn't have enough capacity, or it had to be cranked up to a point where the noise would be intolerable to the people living there. I have a one-way system, an air pump that sucks air in through vents and out through the ceiling in a few points; I have it set to the…

I think this is conflating possible fuckups by the developer - like i stalling undersizer or poor quality system- with inherent disadvantages of the technology

Re: Detailed Assemblies for an Airtight Small Home

#70

Post by namibj »

robocat wrote: post #64
hedora wrote: post #19

Earlier quoted context omitted.

The cost of the fan is dwarfed by labor, and you’re not getting a fan you want to live with for $20. Also, at least in California, you have to hook it to a janky humidity sensing switch that costs more than $20.

> humidity sensing Anyone have links to working designs for humidity controlled fans or similar - preferably Raspberry Pi? I want an indoor sensor and an outdoor sensor, and to run the fan only occasionally (maybe 10 minutes a day) and only when outdoor humidity is much lower then indoor humidity. For holiday sleepout, that sometimes gets damp, but outdoors is sometimes high humidity so no point running fan in that c…

BME680 sensors for temperature/humidity/pressure should be suitable. Consider the PI's PWM output and a hobby RC BLDC motor/controller combination for "cheap variable-speed fan", or alternatively, a large diameter PWM computer fan from e.g. Noctua. Depends on the power class you need/want to go for (PC fan is low power, RC BLDC is high power).
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