Looking for ductless HVAC options for medical reasons
We are building a new home in SW Virginia, climate zone 4a. (3500-4000 HDD, with less than 150 CDD) Not a lot of demand for AC, but we often have high humidity.
Not a passive house, but it will be tight and well insulated. Planning a closed crawl space.
Only 1,300 square feet rectangular single story home, with less than 18,000 BTU heating needs. East half of house will be one large room (kitchen, foyer, den, office niche, living room). West half of house has hall leading to utility room, 2 baths, and 2 bedrooms.
We have no access to natural gas, and propane and heating fuel costs are similar to or more expensive than electric resistance heat. Fortunately, our electric rates are relatively low (around .09 kWh). I am too disabled for wood heat, and we are too shady for much passive solar.
I have extreme sensitivity to mold, some chemicals, and other things. So if we end up using any kind of heat pump or mini split, I need to be able to clean the cooling coils regularly to eliminate any mold growing on them. Doable for most mini splits, but often nearly impossible with regular heat pumps, I think.
We are also trying to avoid using any ductwork, unless it’s round and small enough for me to clean myself. I can’t risk having professional equipment brought in that has cleaned other moldy homes.
As for ventilation, I’m considering using a pair of Lunos fans for our bedrooms, and a bathroom exhaust fan for the rest of the house.
It would be easy to use a mini split for the main room of the house. But the rest of the house is separated with a hall and doorways. And the bedrooms are less than 120 sq ft each, which I’ve been told is too small for individual mini splits.
Any ideas on how to heat and cool the west half of our house? I suppose baseboard heat and window AC is possible – though pricey and noisy. Thanks for any suggestions.
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Replies
Just a couple of thoughts and suggestions...
You should work with an independent HVAC engineer who is experienced with mini splits. For comfort and humidity control, you want an accurate Manual J. If you are building a "pretty good" level of house, the interior temperature should be fairly consistent.
The Daikin Quaternity series of mini split would be worth considering for your project. It has multistage air filtering and onboard humidity control.
We have a couple of Fujitsu minisplits. Filters are easy to clean regularly. Once a year we have the installer totally clean each indoor and outdoor unit. Doing it ourselves would be pretty messy.
As for ventilation, we use a Zehnder HRV, that takes a MERV 13 filter, approximately equivalent to a HEPA filter. I'm not sure what sort of filtration the Lunos offers.
You might discuss placing another minisplit in the hallway with the HVAC consultant Steve suggests you engage.
For the bedrooms it's sometimes reasonable to use a mini-duct cassette type mini-split with the cassette mounted between two bedrooms with essentially zero lenght (less than 2 fee) ducts to split the output between two low load rooms.
Those are some good suggestions, folks. I appreciate it, and will look into them.
Debra,
I would like to know what you found/decided on. We live in Hawaii and researching similiar issues. Our home is very leaky, but would like to be able to control humidity 75% or so).
Andrew
Its very difficult to size equipment to take care your amount of humidity because of the poor airsealing. Constantly changing humidity, pressure variations from day to day, etc.
Tightening up the house results in mind blowing changes in comfort levels!
Once tightening is completed, humidity control is EASY!
It would pay MANY times over to seal leaks and tighten the house
Interesting.
I do not understand as yet the varying demands created by the changing atmosphere. I suppose there is a way... how can one measure the "air tightness" of a home? I assume we are very leaky, but not measured it. The home is a 1960s home, so that counts against us by design. I have used dehumidifiers and they seem to drop the humidity low without any problem.
I have not spoken with AC installers yet. I am concerned about finding the right brand first --- specifically to dehumidify and prevent mold buildup inside the condensor unit.
A blower door test will measure the air tightness of a home using a standardized process that allows you compare your home to others. Energy raters can perform this test for you and so can some HVAC contractors. It’s often better to have an energy rater do the testing since they will tend to be more experienced with the test and less likely to try to sell you new HVAC equipment “solutions” to whatever issues they find.
Bill