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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

#71

Post by de_huit »

kqvamxurcagg wrote: post #69

Is there a risk of condensation, damp and mould from homes with excessive insulation? Perhaps someone with some experience could comment.

There is extra risk of course.

Good ventilation is required through a counter-flow heat-exchange. This typically gives you the problem of too low humidity, as you remove humid air and get condensation in the heat exchange.

There is risk of condensation in the walls. The internal warm layer is airtight, but the walls need to be ably to breath to the outside. Your wood can rot if you make mistakes here, especially on small leaks in the airtight layer. So air-tightness actually is needed to prevent too much condensation in the construction.

This all supposes that warm is inside and cold outside, as is typical where I live. In reverse conditions, with hot humid weather and cooling inside, condensation is likely in the walls, as the airtight layer is on the cold side of the wall now.

So condensation in the construction is unavoidable. I used an online calculator to decide my material use [1] to estimate how often it does happen, and how long it typically takes to dry. Inside my home, I need a humidifier, this winter it was often below 30%.

[1] https://www.ubakus.com/

Re: Detailed Assemblies for an Airtight Small Home

#72

Post by twarge »

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?

Yes, these are energy recovery ventilator (ERV) units. They exchange air while keeping both heat and humidity in. They are absolutely critical to health in tight house construction.

Re: Detailed Assemblies for an Airtight Small Home

#73

Post by twarge »

londons_explore wrote: post #61
HPsquared wrote: post #57

Earlier quoted context omitted.

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 d…

Sensors help, but this is just a fan, and it needs to be on all the time in my experience.

Re: Detailed Assemblies for an Airtight Small Home

#74

Post by rubidium »

anon23anon wrote: post #18
VectorLock wrote: post #6

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

there's another article on that site where she talks about price - it costs her 320k but keep in mind that didn't include the land, her blue prints or all the sweat equity she point in.

Just over 2x standard price it seems given the materials and labor.

Re: Detailed Assemblies for an Airtight Small Home

#75

Post by ClumsyPilot »

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 problem is not that people are idiots, the problem is nobody knows or cares anout what is happening in a rented apartment.

This apartment is owned by a company registered in a tax heaven, he can never be reached and never replies.

The management company does not know anything about the house, how the heating work, how the ventilation works - you only find out on the builsing whats app group from the one guy in the whole building who is a homeowner.

Half the people in this building had a broken ventillation system (the circuitboard died every year, 'luxury' apartments, yey!) and they did not know. This apartment had a broken ventillation system when i moved in.

The previous apartment had a ventillation system too, also was broken, landlord lives in country but has no clue what it is and took 6 months to fix it.

Why boilers have been standard for some time, and everyone knows how to use them, the ventillation systems are all different and most peolle have never seen one before.

Re: Detailed Assemblies for an Airtight Small Home

#76

Post by adrianN »

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.

Humans have relatively reliable CO2 detectors built in that wake you up before you die.

Re: Detailed Assemblies for an Airtight Small Home

#77

Post by b112 »

twarge wrote: post #73
londons_explore wrote: post #61

Earlier quoted context omitted.

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 d…

Sensors help, but this is just a fan, and it needs to be on all the time in my experience.

This sounds like teflon, approved because it is organically safe until it reaches a certain temp, even for a second, then it releases toxic gas, and becomss permanatly harmful to cook on.

The approval logic was, people will:

- always be very careful cooking, and never ever let the heat get too high

- people will learn about teflon, and keep watch

- people care

Meanwhile, stories abound of people's birds dying from toxic gas (they are more susceptible, and die first).

Note that if a bird dies, and you don't, that doesn't mean you were not injured. Or your family.

If you're giving anything to a consumer, assume they know nothing, that they cannot follow directions, won't care even if they understand, etc, etc.

Because that's how it is.

This is validated, proven, over and over and over again.

I love the idea of airtight, but think it is like lead in pipes. If we build like this, kids ... with their developing brains and bodies, will pay the price.

And 40 years later, we'll be astonished at the absurdity of it all, the lost potential, wasted lives. Just like lead pipes, paint, etc.

Re: Detailed Assemblies for an Airtight Small Home

#79

Post by frosted-flakes »

georgeoliver wrote: post #38
m0llusk wrote: post #26

It seems like this could use some testing. How do we know that this really works even in one home? There should be some sensors and metrics to show how well variations work so that the design can be robustly optimized.

Good point, it seems from my perspective the industry is focused on blower-door tests and air exchange, where it's then kind of assumed that "you're done". I don't think there's real incentive at this point for residential building intelligence. We might have to wait for the 2nd (3rd?) wave of smart home tech to make it happen.

Fine Homebuilding ran several articles about installing long-term sensors inside walls in various places around a house that could potentially be troublesome. This was a year or so ago. These sensors (humidity, moisture, temperature, etc.) continuously reported their measurements to some sort of service the homeowner and builder could keep an eye on for any irregularities. The sensors were pretty low cost, if I recall; a few hundred dollars altogether. But its definitely not a common practice.

Re: Detailed Assemblies for an Airtight Small Home

#80

Post by sidewndr46 »

While always neat to read about, I have no idea how you'd ever build one of these homes where I live. If you look at new construction, the poor quality work usually means the the home doesn't even meet the existing weatherization standards. Not to mention you'd have to convince an inspector that everything done is to code.

While I'm always impressed with such structures, they seem mostly out of reach for someone living in suburban america.

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