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caducus
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# Posted: 18 Mar 2018 08:33pm
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I'm building a small cabin in a very temperate climate (Average 45-80 deg). It's 14x20, has a flat shed 3/12 shed roof, made from SIPs. No attic, no rooms, just a box with a loft. It'll be built, not quite to code, but to modern building standards. A wood stove. No other heat or A/C.
So I'm wondering if I need to put some vents in the walls. I realize a building isn't quite air tight, but I still wonder about air circulation for humans and also whether there needs to be air flow for the sake of the building.
Any advise?
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Just
Member
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# Posted: 18 Mar 2018 09:50pm
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If you have a contained attic then yes you need to vent that space . If all one space then a few windows with screens should do it .
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caducus
Member
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# Posted: 18 Mar 2018 10:30pm
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No attic. No soffits. None of the usual things that get ventilated. Lots of windows, with screens. But my concern is that those windows are closed most of the time. No need to have any other sort of ventilation?
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Atlincabin
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# Posted: 18 Mar 2018 10:38pm
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SIPs can be pretty tight. Really depends on how tight your build is overall and how much air exchange occurs (through seepage, opening doors/windows, etc.). A really tight (and small) building can end up with some pretty stale air if there is no exchange. Sounds like you have plenty of windows and screens, so I don't think I would worry too much about it particularly if you are in a temperate climate where the windows are likely to be open or cracked much of the time.
Just my opinion. Might be worth talking with some local building contractors who specialize in SIPs type construction. They might be able to provide more insight.
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caducus
Member
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# Posted: 18 Mar 2018 11:27pm - Edited by: caducus
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SIPs just on the roof, FYI. regular framing on the walls.
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Eddy G
Member
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# Posted: 19 Mar 2018 09:36am
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Why wouldn't you vent it?
Your leaving a lot of info out of the equation but why wouldn't you just add a vent at the top just under each peak?
What would that hurt?
I'm guessing your worried about a draft or something...
First off if the cabin where un-insulated I'd say NO, you do not need a vent.
But as soon as you insulate or close the walls or ceiling up then YES, you should vent it some how....
If it is the draft your worried about you could put a simple set of dampers over the vent and either manually open and close them or wire in a humidistat.....Cost of venting the place is way way way cheaper then the damage and danger you can do by NOT venting it....
It doesn't take a whole lot of condensation to get things started...Microbial growth, mold, moisture, wood rot, etc....
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Steve_S
Member
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# Posted: 19 Mar 2018 10:40am
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With wood burning or gas/lpg appliances you will want controllable air intake / exchange to occur especially with a reasonably air tight cabin. Now if you were to buy an RV Approved / Certified wood stove which allows for an air intake from outside, that could resolve "that" issue but overall liveability, air condition (quality of air) you will want some sort of air exchange happening. Heat Recovery etc are relative to your climate zone and some other choices but from your description I don't think that is a primary concern for you, just direct air exchange would likely be sufficient.
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caducus
Member
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# Posted: 19 Mar 2018 11:48am
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Eddy, "Why wouldn't I vent it?" That's what I'm asking. I literally don't know if I'm supposed to or not, not wondering if I can get away without doing it.
There are no two peaks. Just a single slanted shed roof. So just throw a couple vents up at the high end and call it a day?
I wasn't planning on installing a air intake for the stove. What do you mean by direct air exchange?
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Steve_S
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# Posted: 19 Mar 2018 12:03pm
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The stove will use up your oxygen and could backdraft which must be prevented. Air exchange is essential in a tight building envelope to keep the air fresh and clear as well as managing humidity / dampness which can affect not only the building itself but your health too. In the summer you can open windows so no issue but when it's cold out & your heating, opening windows isn't terribly smart.
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rockies
Member
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# Posted: 19 Mar 2018 07:43pm - Edited by: rockies
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I am using SIPs for my roof and floor (not the walls). My cabin also has a shed roof at a 3:12 pitch, but no loft. Mine will be year round so the heating and vent system will probably be more substantial than yours.
That said, SIPs are very air and moisture impermeable. They can have the effect of turning your cabin into an insulated picnic cooler. The moisture inside has no way of getting out easily.
You should definitely put some venting awning windows up near the roof line in the lofts back wall, not side walls). When open these will create a thermo-syphon effect across the cabin (especially if you have a couple of small vents down low to the ground on the opposite wall. The thermo-syphon will draw the air upwards and help remove interior moisture as well (plus a loft can get unbearably hot without venting windows).
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Borrego
Member
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# Posted: 19 Mar 2018 08:55pm
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Always. Vent. Everything.
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gcrank1
Member
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# Posted: 11 May 2021 08:09pm
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Ive had to vent both of my cabins, and both as an afterthought when the summer heat started stacking downward.
Dump the heat out the vent(s) in the highest point and draw cooler air in low on the shadiest/coolest side or even from under the floor. Dont forget insect screening and that it reduces air flow, so go bigger on vent size than you think.
Having a fan moving air inside is a big help for comfort, beats sitting there and sweltering in still air.
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mj1angier
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# Posted: 12 May 2021 09:32am
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I use a fan like this at the highest point to pull out air,
https://www.amazon.com/gp/product/B07D3QSC2Z/ref=ppx_yo_dt_b_search_asin_title?ie=UTF 8&psc=1
and crack a window.
But when we are not there, we close it up tight and use damp rid to keep moisture down. We are ib a very damp spot so no matter how often you exchange air, you would get mold on surface inside. So being of grid and not being able to us a dehumidifier, damp rid was the only way to go.
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