OAK thru the crawlspace.

[tlhfirelion]

Mornin everyone. We’re about to pour the concrete on our 1600 sq ft ICF house. I’m considering using the crawlspace as the source for the OAK. It’s the size of the house obviously, 4’ tall and will have temp and humidity controlled vents on it. Is this acceptable?
Thank you.

 

[Starbrightsteve]

Mornin everyone. We’re about to pour the concrete on our 1600 sq ft ICF house. I’m considering using the crawlspace as the source for the OAK. It’s the size of the house obviously, 4’ tall and will have temp and humidity controlled vents on it. Is this acceptable?
Thank you.

I think it would be fine to duct through the crawl space to the outside for your air supply. Back when I worked for a living, I spent a considerable amount of time laying down vapor barriers and insulating interior foundation walls and sealing foundation vents. I considered the crawl space to be an unconditioned portion of the interior of the house.

 

[maple1]

Do you mean it would have vents to outdoors? I was thinking that would be a conditioned part of the house envelope - with an ICF build? No direct experience with building with ICF though.

 

[Starbrightsteve]

Do you mean it would have vents to outdoors? I was thinking that would be a conditioned part of the house envelope - with an ICF build? No direct experience with building with ICF though.

You said in your first post that the crawl space would have “temperature and humidity controlled vents”. I assumed those vents were in the foundation wall between the crawlspace interior and the outside. I have very little experience with ICF construction. Most of my work was on 20 to 120 year old wood framed houses. Tell me more about these vents you mentioned. I think the crawlspace should be sealed airtight from the exterior and thus the need to duct through the foundation wall for outside air.

 

[tlhfirelion]

https://www.tjernlund.com/crawl_space_ventilation.htm there will be 3-4 of these in the exterior walls of the crawlspace. So not conditioned in the strict sense of heated and cooled like the home, but not passive cents or closer up tight. I do plan to put down a thick vapor barrier and seal off the ground, where it’s attached and taped to the ICF walls.

 

[moresnow]

Out of curiosity? Why not build on a concrete slab with insulation underneath? What does a unusable crawl space with a dirt floor do for you? Just wondering.

 

[tlhfirelion]

Out of curiosity? Why not build on a concrete slab with insulation underneath? What does a unusable crawl space with a dirt floor do for you? Just wondering.

I’d rather not get off topic here but I’ll answer what reasons moved ME towards a crawlspace. Multiple reasons. Easy install and access to utilities being a big one. Also We’re on a slope and The crawlspace area is not unusable. Once I line it, It’s a great place for storage of kayaks, bikes, Christmas decorations, large tools that are seldom used, etc. etc. We had this in our last house and it proved quite handy for storage, to repair busted water lines, run extra data lines, etc.

 

[electrathon]

Out of curiosity? Why not build on a concrete slab with insulation underneath? What does a unusable crawl space with a dirt floor do for you? Just wondering.

Construction is done differently in different parts of the country. In my area (Portland Oregon) slab on grade construction is considered undesirable. Your question is sort of like asking why use trusses that form an attic when you can build a flat roof. Local codes and design styles vary. As a direct answer, many reasons. Future alterations/repairs are way easier if you have a pathway to run wiring, plumbing, ventilation and etc. A huge issue in many areas is also radon. People die from it and slab on grade is a primary way for it to enter your house. Yes, you can sometimes control it with subsurface ventilation, but it is far more controllable with a crawlspace than it is with a slab.

Edit to add: I did not respond fast enough and tlhfirelion already posted so in order for this to not be a total hijack:

I think the crawl space is a great spot to draw air in through, as long as there are not vents pulling the area into a negative pressure area. It will work like a radon vent system. It does sound more like a walk in basement than a crawlspace from your description though. I cant imagine getting a bike or a kayak into most crawl space entry points.

 

[maple1]

As I mentioned before, I have no experience working with ICF. But it just seems to me that everything within ICF walls should be part of the conditioned & heated interior space. IMO ICF walls are great & you can't get much better for solidness, tightness & insulation value - so just seems off to me to have a crawl space at the bottom of that exposed to the outside.

I would likely go at it as treating the 4' space, as a short basement. With an insulated concrete floor at the bottom, and all part of the envelope. Especially if there will be plumbing under there.

(I could still me missing something - and sorry for the further derail...)

 

[begreen]

I’m considering using the crawlspace as the source for the OAK.

https://www.tjernlund.com/crawl_space_ventilation.htm there will be 3-4 of these in the exterior walls of the crawlspace. So not conditioned in the strict sense of heated and cooled like the home, but not passive cents or closer up tight. I do plan to put down a thick vapor barrier and seal off the ground, where it’s attached and taped to the ICF walls.

Definitely no. Those exhaust fans would work against the stove trying to pull air from the crawlspace. It's keeping negative pressure in that area which would be dangerous if it reversed draft on the stove. The stove's OAK should be ducted to the outdoors through the wall, either in the crawlspace or at the stove level.

 

[tlhfirelion]

Definitely no. Those exhaust fans would work against the stove trying to pull air from the crawlspace. It's keeping negative pressure in that area which would be dangerous if it reversed draft on the stove. The stove's OAK should be ducted to the outdoors through the wall, either in the crawlspace or at the stove level.

I do believe you’re correct. I plan to go straight out the ICF wall behind the stove. I assume a 6” opening will be adequate or do I need to go larger? Thanks for everyone’s replies.

 

[bholler]

I do believe you’re correct. I plan to go straight out the ICF wall behind the stove. I assume a 6” opening will be adequate or do I need to go larger? Thanks for everyone’s replies.

It is usually 3" sometimes 4" so I would put a 5" sleeve through the forms