HVAC Upgrade/Modification For Increased Comfort
I’m looking for some advice regarding our HVAC system, or otherwise regarding some improvements we could make. We are looking to build a house in the next few years, but we will be here in the meantime, and I spend a lot of time here (WFH). The house in question is a 1960s single story ranch, around 950sqft with a basement. R11 in the walls (guessing), R49 in the attic. And the attached garage shares a 24ft wall, and is heated/cooled with a heat pump. Windows are newer, but low dollar horizontal sliders. Detroit – climate zone 5.
For equipment, nothing is that old. I have a 13 SEER 2 ton AC, and an 80% 80,000BTU furnace.
For load analysis – I used a Borst calculated to estimate around 11,000 BTU total heat loss. 8,000 being sensible and 3,000 being latent. Using the furnace sizing article on GBA, heat load comes in around 13,000 btu/hr. This was lower than I calculated with Borst, and lower than I anticipated. I calculated for a few different periods and got roughly the same result.
Now that issue I’d like to address in order of importance to me.
1) Summer humidity – even with the indoor temp at 69-70*, humidity is often above 60%. I’d rather drop humidity and increase the temperature to ~75. Not surprising with my AC system. It’s often in the 70s outside with thick enough air you can swim instead of walk if you prefer.
2) Cold kitchen floor – I often sit at the kitchen table for work all day. The tile floor here stays pretty cold, 65* or so. It’s right in front of a (bottom dollar Anderson) sliding glass door (“doorwall” as they say in Michigan). The air gets a bit cold too when the heat is between cycling.
3) Basement heat distribution – We have a finished basement, and the far end of it has no vents. There are 3 total vents in the basement, and one poorly placed return. The far end of the basement gets fairly cold with no air movement. My thinking is a return here would be a huge benefit.
So obviously my equipment is way oversized, and that’s probably a big part of it. When I moved in, I wasn’t that educated in proper design, and just upgraded the attic from R8 to R49 (blown cellulose). With R8, my equipment might have decent run time… In the shoulder seasons, like now, it’s cycling on only for a few minutes at a time. My ductwork is run below the floor joists, so all in the conditioned area. I cut and cobbled together insulation in the rim joist below the kitchen to try and improve that area. I didn’t do the whole basement however.
Now, given all that, I’m not interested in doing a huge tearup here. Ideas I had that address some or all concerns:
Single minisplit head in the livingroom/kitchen area – keeps air mixing and should help the humidity issue if sized appropriately.
Standalone dehumidifier – ducted or just in the basement.
Replace furnace/AC with a ducted heat pump -this seems like it would be more expensive than it’s worth, and we do have good condition equipment as is from ~2016.
Small electric heater of some sort near the sliding door. I don’t really want a mobile unit, I’d prefer something more permanent and out of a toddler’s curious reach.
What would the community suggest? Thanks!
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