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Comment by leguminous | Hacker News Reader

Air sealing is also critical. The insulation can be defeated if unconditioned air can leak into the house and conditioned air can leak out. It's a difficult thing to get right because it requires attention to detail and if done poorly it can result in moisture problems.

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Are there no health issues associated with a house being that well sealed, or do you have some sort of air exchanger that is temperature efficient?

Edit: e.g. googling brought up this article - https://www.architectsjournal.co.uk/buildings/airtightness-b...

You insulate and air seal properly, then make sure that you bring in outside air in a controlled fashion (enough CFM, filtered, etc):

* https://www.youtube.com/watch?v=CIcrXut_EFA

I wonder what carbon dioxide levels get up to in a well-sealed house.

You’ll want mechanical ventilation (with heat recovery) to prevent that: https://en.wikipedia.org/wiki/Heat_recovery_ventilation

Heat recovery + well sealed house with some humans inside can potentially mean no heating at all!

Some good comments on that in this HN thread from a few weeks back. In short, not good.

https://news.ycombinator.com/item?id=18959796

Thanks for the link.

shouldn't houseplants be sufficient?

For anyone interested, Building Sciences Corp is a great resource on different methods to build functional, airtight, well insulated walls. Here's a starting point:

https://www.buildingscience.com/documents/insights/bsi-001-t...

I'll add https://greenbuildingadvisor.com for a site that has a lot of quality discussion and analysis on energy efficiency for buildings. The forum and comments can teach you a lot.

I wonder how feasible maintaining that is? I feel like it's very common to find people who work on your house will mess this up (cable or satellite dish installers, for example). That seems to happen for everything, but it depends on the resiliency. I bought a house where satellite dish installers drilled right through the shingles, likely compromising the water permeability of the roof. Ironically, I had heat pumps installed last year. Soon after I had rodents. I feel like they did a good job of weatherproofing exterior holes they made, but after patching up the crawlspaces the rodents disappeared.

People are grossed out by rodents and a leaky roof has to be addressed, but if their heating/cooling cost goes up slightly because a cable installer messed up are they going to hire someone to hook up a blower door, patch things up, and charge this back to the cable company?

It's hard, but the BTU loss from a 10'x 10' uninsulated wall is equivalent to a 1"x 1" hole in an R-31 wall.

There really is just a severe lack of building science education in American construction, because the margins are so thin and it is still dominated by blue collar "man in a van" companies. So you have boneheaded contractors drilling holes into air barriers because that's how it's always been done.

Interesting thing is a lot of sound deadening practices also apply to insulation. I don’t know if this statistic is accurate in the audio case but it’s not far off.

Heat conduction through studs in an insulated wall also carries sound. A 2x6 plate wall with 2x4 studs on alternating faces (think slalom) helps with both.

I just had a minisplit head installed at my house, and when they used a hole-saw on my external wall, it basically trashed the fiberglass insulation in that stud cavity.

Fortunately this was part of a project to finish my home office, so I still had access to the space between the internal and external walls. Not only could I see the insulation damage, I could also repair it without too much effort.

But in general, I agree there's a responsibility gap when it comes to these installers. I think the best practical solution for now is to factor into such projects the cost of restoring a building's thermal envelope.

EDIT: I should mention that a blower-door test might not have detected this damage. The cavity whose insulation was damaged has pretty good draft-blockage from the rest of the house, due to fire-code requirements.

> But in general, I agree there's a responsibility gap when it comes to these installers. I think the best practical solution for now is to factor into such projects the cost of restoring a building's thermal envelope.

What, $5 for a tube of exterior grade caulk? Vapor barrier seal tape is 10 cents a foot. Add in $10 in labor per penetration and you're done.

You could leave it out of your estimate entirely and not even notice if your guys did the work.

edit: I'm a commericial construction estimator

Maybe I used the term "thermal envelope" too loosely?

I agree that restoring an air seal is trivial on a per-hole basis. My main point was restoring the lost insulation performance that comes from trashing one stud cavity of fiberglass batt insulation when the hole is made.

Based on my limited knowledge, I don't know what impact that might have on the overall structure's thermal efficiency. I would also worry about risk to any water-carrying pipes running through such a section in a cold climate.

If the drill snagged the fiberglass and spun and compressed it creating a large void, it's certainly going to be much more than caulk and tape to repair and restore.

Right. In my case the strip of fiberglass batt was basically flopped over in that section. (It's a double-framed wall, so there was space for the batt to fall away from the outer wall.)

That high efficiency envelopes are brittle is something that concerns me. Cold air and water needs to be kept out, but more importantly water needs to get out or you get major damage that will completely negate any energy savings.

In the Midwest there is an utter catastrophe where modern high efficiency houses are rotting away because construction and design errors let water in or water to condense with no way out.

It is indeed critical and all new houses in Sweden are tested for leaks under pressure. Those that leak sufficiently little get to call themselves Passivhus and you have some taxation benefits.

A handful of US states have also made blower door testing mandatory in new homes, but we still have a long way to go. A few states don't even have state-wide building codes, much less efficiency requirements.

How do they test that?

At least in the US, blower door testing:

https://en.m.wikipedia.org/wiki/Blower_door

I've had this done before, very, very informative. Those machines are like $3K to buy, you can hire someone to come out and do it, but this seems like a perfect DIY project.

An other very informative thing to get done is thermal imaging of the walls (from inside and outside both). Very good at uncovering damp spots and water infiltration too.

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