High Performance Home HVAC Needs Balancing, Contractor Limitations
I built a high performance home in Zone 7 Northern Wisconsin, finishing it in summer of 2022.
We installed a Mitsubishi SVZ-KP30NA Air Handler and a SUZ-KA30NAHZ condensing outdoor unit. The air handler is ducted throughout the house with a duct plan provided by a 3rd party mechanical design firm.
I have Renewaire EV-L Premium ducted into the air return for fresh air distribution throughout the home and then dedicated exhaust.
Here’s what’s going on:
1. The main floor is fine, even with many registers closed. The temperature is very equal since it is such an insulated house. The upstairs is too warm in the summer and winter and never seems “fresh enough.” The air is stale. When you put your hand over ducts upstairs, it seems like almost no air is coming out. The contractor acknowledged upon completion that “it was hard to get the air up there” but of course, I didn’t know what that meant at the time.
3. We’re over-ventilating with the ERV (see https://www.greenbuildingadvisor.com/question/zone-7-new-tight-house-excessively-dry), but I don’t want to dial it back yet until the overall HVAC is balanced since fresh air is carried via the same ductwork.
– I’ve tried dialing back the balancing dampers a little bit and closing off registers to get more air to the upstairs. That doesn’t seem to make a big difference.
– I don’t have confidence that the original contractor can get this balanced properly given that they were puzzled at the original commissioning.
– The ductwork is generally pretty close to the design. There are some cases where there is some “can of worms” arrangements going on. See attached for examples. There are a few additional bends, turns and such, but it isn’t excessive.
– They didn’t follow the register and boot sizes–nearly everything is a 2×10. The plan had called for different sizes all over the place.
– Originally they didn’t even put balancing dampers in. I required them to add them. They installed most balancing dampers near the boot in most cases though and not near where the duct breaks off from the trunk.
– They added (2) 90s and then 8’x2 at the end of the entire system run (the upstairs bedrooms) where the registers were supposed to be right off the trunk with no additional lengths. So that didn’t follow plan.
What should I look at?
– Just play with balancing and dialing back vents that are closer to the air handler to push more air? I’ve tried this a little bit and hasn’t seemed to make a big difference.
– Duct tightness/leakage–should I go over all of their joints and seal better?
– Eliminate duct and branches in rooms that haven’t had any temp control issues? For example, our main space has 6 registers and I could probably close a bunch of them and have no heat/cool issues.
– Move balancing dampers closer to the trunk?
I admittedly don’t know a lot about HVAC, however, I did build the entire house myself and am generally handy.
Do it myself, find a contractor, work with someone from afar?
– I don’t have any experts in my area but there are people who have vent hoods and a general knowledge.
– I dont’ have the equipment but if the best solution is to learn this myself, I will.
– I did make contact with an expert several hours away (who writes for Fine Homebuilding) that said they could come and help, but they wouldn’t be a long-term contractor solution.
Thank you so much for your help, as always!
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