If you could only choose one this year - Insulate crawlspace or Seal ducts?

I'm not crying about it, just doing something about it. Here's an idea: wouldn't it be more productive in life to say : yeah, I feel your pain, instead of nit-picking and pointing out everything that is not to your liking while saying "I could of done it better" under your breath.We all have special things in our environment that we deal with. Telling someone they are dumb for building low (when a whole land area is low) is like me telling you that you should of built underground the next time St. Hellens Blows.

Yeah the crawl might get a foot of water now and then but it does move after a few days. One would need a whole lot of dirt to build up a foundation/$$ to jack up the house. The water would still find it's way back up because the back pressure on the ditch would "push" it up". Sounds crazy, but you can go out in the field and see this happening.It's just not financially possible to jack up the house. (unless you're paying?) Oh yeah, here's some photos from some of our rain. While this isn't my house, very similar situations. It get's crazy sometimes in NW OH when it starts to rain. You have to be here. It's one of those things, either you can understand it or you call us crazy.This will be my last post...let's get back to talking about wood.


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OP, what did you decide to do? It seemed like a tough decision.

If you have to choose only one to do at this point, I'd choose insulation. get that stuff done first, to help with heat retention. Heat loss through your house only aids in helping the drafts get stronger. do the ducts when you get time/money to do so.

Not to threadjack (only a little) ... But I am here in North Carolina - where the seminal, I think, study on this topic was done (by Advanced Energy). Long before that, I decided that I should leave my foundation vents closed, and even without anything close to an "encapsulated" crawlspace, it helped - a LOT. But I've decided to get more serious about really air-sealing the crawlspace.

What I'm really not sure about is whether or not to insulate the foundation walls. My floor (between the house and crawlspace) is well-insulated with fiberglass batts, so I don't need to, for code or anything. The AE paper shows a slight improvement from insulating foundation walls versus insulating the floor (18%, rather than 15%, energy savings over old-fashioned vented crawlspace). But it seems to me like the improvement should be MUCH greater than that. For my fairly typical house, the square-footage of the foundation walls is roughly half that of the floor - so insulating them to a similar R-value should halve the heat loss through the floor of the living area. But additionally, the HVAC ducts are in the crawlspace. Lord only knows what the square footage of all the various HVAC ducts and returns and plenums is, but I'll bet it's a lot. An with an insulated floor, they are also a source of heat loss. But with insulated foundation walls, effectively moving the HVAC ductwork into the conditioned envelope, that source off heat-loss is eliminated. So it seems like the energy savings should be far greater than 18% versus 15%.

Still, the bid I have is $1850 for just sealing the crawlspace, but another $2000 for insulating the walls. So I'd like to be assured the energy savings will be greater before spending the extra $$$.

It doesnt seem complicated to me. Build above the water line. Though in this case Id say you should insulate the floor.

One quick question Rusty: is the floor really well insulated with fiberglass? Most fiberglass installed between floor joists is not done properly. The batts are placed between the joists so that a gap exists between the fiberglass and the subfloor above. The batts need to have full contact with the floor above to be truly effective. This is really tough to achieve with fiberglass as it settles with time; one reason that foam between floor joists is more common now.

There are other major considerations with respect to encapsulating your crawlspace. You mention thermal insulation and the ducts, important issues. However, I'd suggest that moisture control may be the most important potential benefit, depending on your conditions. Even well ventilated crawlspaces may harbor nasty molds, etc. and with ductwork in the crawlspace its not too hard to see it making its way into your living space.

We are leaning towards doing the insulation now, ducts next year. We mainly heat with wood - though part of why we do that is that the ducts are so leaky the heat doesn't get to the upstairs anyway. So duct sealing would give us a good backup source of heat - but it can fall by the wayside I guess until next year. I liked that the duct sealing guys were offering $500 discount this month, but I guess if we have to choose one, it will be to insulate.

HOWEVER, we're going to have to do batts in the two smaller, more reachable crawls, and foam in the big one that's so claustrophobic. To do all of them is like $7K, revisiting the estimate. Ugh.

Good point and question, and I'd say your suspicion is correct - the floor batts aren't all that well installed, and they are sagging a bit (25 years later).

Also, one of the main reasons I'm addressing this issue is that I'm doing a small addition - so I can go either way with it. But I probably don't want to omit floor batts in the addition if I decide not to insulate the foundation walls of the entire crawlspace (since the addition crawlspace is semi-open to the existing one).

Oh yes, absolutely; moisture control is the main reason I'm doing this. But that can be achieved by encapsulating the crawlspace, whether or nor I decide to insulate the block wall or use fiberglass in the floor - the latter is an independent decision, I believe.

But the additional cost of insulating the walls is about $2100. Minus the cost of putting batts in the addition floor. But plus the cost of removing the batts in the existing house - I guess I don't have to do that if I decide to insulate the walls, but seems like a good idea. I don't want to spend that $2k or so unless I'm gonna save some energy too. What I'm not sure how to factor into the equation is the floor of the crawlspace. I'm pretty sure it'd be impractical or prohibitively expensive to insulate that. The ground seems to be pretty cool - so I'm thinking it's a net plus (to have the conditioned space un-insulated from the crawlspace floor) in the summer, probably a slight minus in the winter. But mine is more a cooling climate I believe (central NC), and my heat is a lot cheaper (dollarwise and environmentally) than my cooling (self-provided firewood versus mostly-coal fired electricity).

Thanks for your ideas !