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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

#21

Post by loopdoend »

tvb12 wrote: post #11
jweir wrote: post #7

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

> "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?

If you have an exhaust fan on to remove shower steam, the air needs to come from somewhere. You don’t want it getting sucked in through the walls (bad air quality). Better to open a window.

Re: Detailed Assemblies for an Airtight Small Home

#23

Post by insaneirish »

VectorLock wrote: post #6

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

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...

Re: Detailed Assemblies for an Airtight Small Home

#24

Post by mypalmike »

ebrewste wrote: post #12
matthewaveryusa wrote: post #8

I understand that the construction materials were chosen to be healthier, but wouldn’t it be even better to have a ‘loose’ house with those same materials?

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 an old house, you will know about the rat poop by the smell after you turn on that new AC unit.

Re: Detailed Assemblies for an Airtight Small Home

#25

Post by ars »

wffurr wrote: post #4
nvahalik wrote: post #2

How well do these operate if the electricity fails? If it’s airtight wouldn’t you eventually run out of oxygen?

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.

Re: Detailed Assemblies for an Airtight Small Home

#27

Post by yjftsjthsd-h »

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.

> Also, at least in California, you have to hook it to a janky humidity sensing switch that costs more than $20.

To make it run automatically?

Re: Detailed Assemblies for an Airtight Small Home

#28

Post by bombcar »

hedora wrote: post #20

We did something similar recently. This looks like standard, low cost modern construction to me. If you’re in a warmish climate (like the SF bay area), you probably don’t want to insulate the concrete slab. You get lots of passive heating of the slab in winter already, and having the ground suck that heat out is a win almost year round. South facing windows can be designed with an eave, etc to lower passive heating i…

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

Re: Detailed Assemblies for an Airtight Small Home

#29

Post by __d »

I'm curious about the "vent chute": the asphalt-coated fiberboard above the ceiling insulation, but set below the roof sheathing. It creates a cavity beneath the roof that is vented through the eaves.

Anyone know why this is done?

Re: Detailed Assemblies for an Airtight Small Home

#30

Post by chuckledog »

yjftsjthsd-h wrote: post #27
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.

> Also, at least in California, you have to hook it to a janky humidity sensing switch that costs more than $20. To make it run automatically?

To have your tight house (and your family) breathe properly you’ll want to couple your smart bathroom exhaust fans with filtered air intakes. HRV/ERVs can do this but are overkill in many mild climates. A set of simple fan+filter pairs does the trick for us, can’t believe we lived so many years in poor ventilation.
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