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Ok, former owner was a flipper/company and jacked up everything, and so now I've found that they ripped out all of the subfloor insulation in the crawlspace and half the blown in in the atticwithout replacing it and the house is quite drafty. I fixed the fact that they had vented the bathroom and kitchen exhaust fans back into the HVAC by putting in temporary pipe vents to the roof, to be replaced with prettier turn-downs when I get time. Additionally, they installed can lights throughout the kitchen and living room, so I'm looking at about a thousand penetrations in the ceiling with the HVAC situated in the floored attic of this single story rancher, meaning I would have to pull up the attic floor sheathing to even begin trying to seal up air leaks.

Attic has soffits, gable vents that are about two feet below the peak, and a ridge vent that you cannot see daylight through(or the light from the outside at night), either because it's clogged up or they just threw the tar paper over the ridge and didn't bother to cut the paper for the vent(brand new roof, and you can see new plywood in section that had clearly leaked before)

Crawlspace, in addition to the same copious amounts of construction debris I found in the attic, has humidity problems and I've already got a dehumidifier working on that with landscaping happening in the next few weeks. As an aside, I work as an equipment operator for a grading company and we are waiting for winter business to slow down before we fix the fact that the house needs a few inches of dirt around it to push the water away from the foundation.

I've been debating on what the best solution here is for both energy savings and to keep myself from becoming a mushroom farmer...

I'm just outside Richmond Virginia, so humidity year round is a bit of an issue, and we do occasionally get snow and very wet winters, so humidity control would likely save a lot in energy costs, not to mention mold damage.

My gut is telling me I should encapsulate the basement with 20 mil vapor barrier and rigid foam insulation, then turn the attic into a conditioned space by installing baffles from soffit to ridge while blocking off the gable vents and then going hog wild on the rafters with closed cell spray foam.

Any experts want to weigh in on this and tell me that I'm either a genius or an idiot?

Also, if I go with the baffles, is there a good way to retain access to the ridge vent from underneath for cleaning?

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Making your house more airtight and more well insulated is a great idea. However the more airtight you make the house (say by spray-foaming close-cell foam on the underside of the roof), the more you will trap moisture inside the building envelope. Things like taking a bath or shower, or even just cooking on the stove, will add humidity to the interior of the house.

Additionally, you will end up with less fresh air inside the house and that means less oxygen and more build-up of off gassed chemicals from manufactured goods in the home.

So, usually, by code, when your house becomes very airtight, you need to bring fresh air into the conditioned space via a mechanical device called a Recovery Ventilator. There are two kinds, Energy Recovery Ventilators and HRVs, Heat Recover Ventilators. ERVs can retain moisture from the interior while bringing in fresh air from outside, and HRVs don't retain the moisture from the interior. Both retain the temperature of the indoor air while bringing in fresh outdoor air.

Here's what I would do: get a blower door test to determine how bad the air leakage actually is, then identify the areas where you think you can make the house more airtight in the most effective manner. Iterate on these things, and then get another blower door test. Add an ERV or HRV to ensure that you can have fresh air.

Spray foam is a great choice, but you need to ventilate.

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