Detailed Assemblies for an Airtight Small Home

Similarly, their parent company, Taunton Press, publishes a number of DIY-er focused home improvement books.

I own a few of them, and I have found every single one to be a worthwhile purchase.

Home ownership is a luxury everyone wants. I can't imagine people don't salivate at the idea of a sturdy, comfortable, private nest. The only class of people who can afford it are people with incomes on par with tech workers.

> You get lots of thermal bridging

The way they did it with those gussets, it seems so. But I don't think double studded walls always imply more thermal bridging than single stud walls where typically every 16 inches there's a complete thermal bridge. I think the double studded wall has proven its effectiveness.

> your outer studs freeze

Well if they don't freeze, you're heating them. So I would think the outer studs should freeze.

> venturing out of one's comfort zone to do an exterior insulated system has enormous durability and performance benefits

Any similarly detailed writeups of this?

>Let's build our homes for centuries, not decades, folks!

I agree with you, but unfortunately the incentives in the system penalize constructing high quality buildings. The higher quality the building, the more taxes you pay.

I agree with your main point but it's worth it to point out that air tightness is only a consideration in climates with really cold seasons. I live in a roughly mediterranean region (Lisbon) and it drives me up the wall to see people spend fortunes on passive-haus-like builds.

Meanwhile my own home is about 200 years old, built out of stone and lime, has no air tightness whatsoever -in fact it had a 5m2 hole in an exterior wall for most of 2020 and 2021- and I'm perfectly confortable with no environmental heating or cooling. Windows are opened every day of the year.

Good design and a good location beat excellent construction any day of the week.

I got one too, and a PM2.5 laser sensor. It's a huge challenge during wildfire season to keep the PM2.5 and CO2 both good. Needs filtered HVAC to actually do it. I prefer high CO₂ over high PM2.5 of course.

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

I need to get into CO2 monitor sales and then some cloud connected device that changes the CO2 levels somehow (maybe just a fan). After that, sell a subscription to adjust the CO2 ppm through a website. People will fiddle with it and pay the subscription for the rest of their lives.

Insulating the slab doesn't matter as much as it may appear, as the ground "below" the house eventually reaches equilibrium. Insulating the side foundation walls can be much more useful.

http://www.sensiblehouse.org/nrg_heatloss.htm

I build homes. This isn't standard in the US. I don't know how much cost it added -- probably not a lot. 10-20% I'm guessing. But, it's not low-cost.

> This looks like standard, low cost modern construction to me.

That's the idea, use as much standard stuff, but in a slightly different way to get a way better result, but similar enough you can use normal contractors to execute.

For example, any framer can make a 2x4 wall. But if you want to use SIPs, AAC, even insulated concrete forms... good luck finding someone in most of the country.

> This looks like standard, low cost modern construction to me.

Have not seen double-stud walls. Perhaps the rest is typical?

It probably would make sense to have controlled and well-managed ventilation in airtight houses. It'd still be more energy efficient to heat and cool at a particular ventilation point rather than have what traditional houses have... a lot of leakage everywhere.

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 the occupant interviews suggest inadequate knowledge of the ventilation system, with all Code 4 homes stating ‘not sure’ when asked about various features of the MVHR system, including the current settings, changing of filters, boost mode function and location of controls.

Knowledge of the MVHR system was considerably lacking in Code 4 homes. All households stated that they did not know where the controls for the system were located, or how to change the settings.

They asked people who moved into "airtight" social housing if they understood how the systems worked to keep the air moving and people said no.

No wonder they had worse air quality...

> "The unit has produced a public awareness film urging people to ventilate their homes properly by ‘keeping vents or windows open when cooking, showering and cleaning..."

Why showering?

Typically with passive houses/"pretty good" houses that have low inherent ACH they then have HRV/ERVs installed for mechanical ventilation, to provide good air quality. It's possible for such a building to have better air quality than normal construction.

At the same time, the theory isn't always embodied correctly. The ventilation design may be poor or make wrong assumptions (like requiring bedroom doors to be open) or the homeowner may unwittingly turn it off or not change the filter periodically.

I have a ~40 year old house that has some energy-efficient features, but ultimately isn't very tight and doesn't need ventilation. I still hope to install an ERV in the next few years, though, just because I think the benefits of good ventilation will be so strong.

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.

I think this dude built it himself. My father in law and my grandpa both built their own homes that they still live in today, neither one had any professional construction experience. Not nearly to this standard, but nobody cared about this sort of thing back the. And they didn’t have YouTube to solve problems.

> the poor quality work

I keep hearing that, but those who are in the trade listen to engineers who have done real analysis. What looks good often is bad, what looks bad is often good.

You can open the door or window.

A single person in an air-tight average sized room could survive on the available oxygen for about a week. So I suppose if you're in a perfectly air-tight room and no one comes and goes at all or opens a window, you could die eventually.

Even if you're relatively reclusive, assuming you go outside once a day to get the mail... you'll be fine.

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/

If you don't analyze it properly there's always the risk of condensation in the walls, but that risk is far higher from uninsulated walls. With uninsulated cavity walls you have room temperature + room humidity on the interior, and a sharp gradient to outside temperature within the wall, where all the moisture condenses in the winter. Worst possible situation.

There's tons of published guidelines about moisture in insulated walls. The easiest thing to build without making some fatal mistake is to put the insulation on the exterior, with a ventilated screen between it and the wall cladding. The best solution also depends on your local climate. See e.g. https://www.nrel.gov/docs/fy13osti/56709.pdf

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).

I disagree. Airtightness is far more important than insulation. Insulation is worthless if air currents can simply carry the heat and bypass the insulation.

And unless you're building an ICF house, some minor thermal bridging is unavoidable. But it does not matter because you can just insulate more somewhere else to make up for it. Exterior foamboard insulation around the entirety of the house is already quite common and cost-effective.

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.

If you are a builder that executes these details on every project, the cost impact is manageable. When you consider that houses are largely financed and also have operating costs that are dependent on energy efficiency, better built homes make sense on a cash flow basis.

However, the real estate industry does not properly value energy efficient projects, and most builders don't execute these details often, so they end up costing more than they should.

Another article from Fine Homebuilding goes over some of these issues: https://www.finehomebuilding.com/project-guides/insulation/d...

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...

I mean to be honest it looks like a doublewide manufactured home, but cost like a 3400 sq ft. But if it's what you like, go for it I guess.

Venting the roof is standard in new construction, to protect the roof structure from moisture and excessive heat. They did the fiberboard chute so they could densely pack blown-in cellulose. Otherwise the insulation wouldn't have a good surface to push against (you don't want the insulation to touch the roof sheathing).

On typical homes with blown-in ceiling insulation the insulators will staple cardboard against the lower few feet of roof framing, creating a similar vent space from eave to ridge.

This home's ceiling R-value of 82 is about 2.5 times standard.

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.

You want to control your ventilation. Making a loose house just means you get ventilation, but not on your terms. HRV/ervs in a tight house allows you to ventilate your house, how you want, where you want. A loose house might be ventilating your house through insulation filled with dust and rat poop. You will never know.

In theory if you get just the right number of air exchangers such that the same amount of air moves through as it would with a 'loose' house, you get the same airflow with almost none of the convective heat loss/gain.

This is however, very much in theory, since as far as I can tell we're still in the early stages of figuring out how to do airtight houses well. My home was built in ~2006 and has an unhealthy CO2 build-up if I close the windows, since it has no active ventilation whatsoever.

You need a ventilation system that recoups the heat of your house. That means you have air inflow in dry rooms, and air outflow in wet rooms. The cold outside air going in gets heated up by the warm inside air going out.

Very efficient way of keeping your house warm. That's why it's used a lot in northern European countries.

>...seeing supposedly intelligent people wearing face masks for health reasons.

Are you including doctors, nurses, vets etc during surgery?