Off grid house ventilation
Hey all. We’re trying to figure out the best method for ventilation for our 20×36 two story off grid house in mid-coast Maine climate zone 6. It’s going to have R-21 timberbatt insulation inside and 3in of polyiso exterior insulation. I did read Martin’s article about designing an off grid house, which is great, but I’m wondering if anyone else has some more input on what they do to ventilate their off grid house.
Mainly we’re looking to keep dust down, control humidity levels, and exhaust cooking smells/smoke. We’ve seen humidity levels as high as 50% inside which leads to condensation and icing (in very cold temps) on the windows. Our only source of heat is a wood cook stove, hence the dust, and the temperature inside usually hovers around 70 degrees. We do crack windows every now and then but when it’s very cold, that’s not really ideal.
We will be starting with a 6kw solar system with a lithium iron phosphate battery. We will probably expand it as needed and/or use a generator for back up.
An ERV is likely out of the question. I was looking into the Lunos e2 but I’m wondering how well those perform in the winter. I read their heat recovery isn’t always great and they may not be efficient at very cold temperatures.
I was wondering about the Panasonic bath fans too. Our house has an open floor plan so I was thinking maybe we could get away with installing one in the downstairs bathroom and using it as needed. Does anyone ventilate this way off grid?
Any other suggestions?
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Replies
Hi,
Why are ERVs out of the question? Is it an energy usage issue? They are fairly efficient. Probably more so than bath fans. What are the constraints other than energy?
I would consider a DC fan running on your battery buss voltage. This is likely to be your most efficient option, but will also likely rule out nearly all commercially made ventilation products.
Bill
I'm designing a 2-story, off-grid house for clients now. I wanted to add a cupola with venting windows, which I think would have worked well, but they didn't like the look. So instead I'm including an ERV. They are recently retired, award-winning chefs so cooking is important to them, and I insisted on having a range hood with a makeup air system. They will need more electricity to run those things, but I have not found a suitable substitute for good indoor air quality.
I'm confused by the 'it's going to' and 'we have seen'
Is this a renovation?
I am surprised ventilation is that much an issue with a wood stove.
The house is dried in and we are currently living in it even though it is unfinished. I should have mentioned that.
The wood stove has a 16 gallon water reservoir we use for our hot water, also should have mentioned that above… eliminating that would keep humidity down but it is our only source for hot water in the winter so I wanted to figure out a way to keep the humidity low even with the reservoir.
For an ERV, I thought Martin’s article mentioned that they used a decent amount of power. The other thing is the house is on a slab and the attic is unconditioned space. There aren’t too many options on where to locate an ERV, unless we created some kind of conditioned space within the attic. Do ERVs help control humidity? I may be wrong but I thought one of their downsides was increased humidity(?).
ERVs running continuously consume a "decent amount of power" over time, but they aren't really large loads aside from their long runtimes.
Bill
It's surprising that a wood stove that is likely pulling a lot of air through the house isn't drying it out by itself. I wonder if your hot water configuration with the wood stove is generating a large amount of humidity. If that's the case, maybe you can find a way to control the humidity coming from that. Is that your maine source of moisture?
Yes that reservoir is our main source of moisture in the house. Other than not having water in it, I’m not really sure how we could keep the humidity down. The reservoir has metal lids that don’t really seal well, I’d have to investigate if there’s anyway to get them to seal better.