Installed a DIY MrCool 4 ton unit in my 110 year old farmhouse for my MIL. 1400-1500sq feet, 3br 1.5 bath, r60 in the original attic but NO insulation in the walls at all. Thermostat says -1.8F but was actually between -6 and -8 last night, it uses a web service to pull local weather. It was able to maintain 65+ with no heat strips and still at a COP of 1.55 so more than 50% cheaper than baseboard or space heaters. This isn't even one of those fancy vapor injection units either, just a $4500 unit with pre-charged no vac quick hookup lines. If the house had anything close to modern insulation in the walls I have no doubt it would maintain 70F below -10F. I may get a quote on insulation injection into the walls to help out.
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For those who doubt Heat Pumps
- Thread starter farmwithjunk
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I went DIY because one quote was $13,000 for less efficient heat pump w/heat strips (I didn't install heat strips) and the 2nd was "Over $20,000" for a new oil furnace with heat pump. House had two 100K BTU oil furnace, one was added for a sun room addition that's only 12x26' and has 28" feet of windows so lot of heat loss.
Not only does that save on heating costs but nearly cuts cooling costs in half vs the ~10 seer AC it replaced going to the 18 seer I installed. Smart thermostat helps too and with min runtimes, min off times and a larger temp differential it has a fraction of the start cycles.
Not only does that save on heating costs but nearly cuts cooling costs in half vs the ~10 seer AC it replaced going to the 18 seer I installed. Smart thermostat helps too and with min runtimes, min off times and a larger temp differential it has a fraction of the start cycles.
Yeah, this is a ducted unit, not a mini-split. I did it entirely by myself including getting the air handler into the basement, etc. There are several re-brands doing this now. Either Gree or Midea makes them.
The lines are more like hydraulic lines with o-rings and they are pre-charged so literally just thread on the lines. I had no interest in nitrogen purging the lines for brazing. Has a 10 year parts warranty too which from reading they seem to support well.
I've installed 2 of them, one with pre-charged lines and another with existing copper lines for a 2nd level.
You might consider having cellulose insulation blown into your walls as an alternative to foam.
If its a similar cost I think the water based stuff is a better choice personally. Sounds like it would be around 5-9K but I didn't get a quote yet. It would have around R18 in the walls if their r values are to be believe plus it would be air sealed. This would be an external application with a row of siding removed for their injection holes.
I spray foamed the rim joists and windows are about 15 years old so really just the walls are left. That would surpass all but the newest homes if I got the insulation done.
With thermal bridging, the difference between foam and densepack cellulose would be small. And the foam is more likely to shrank away over time (making the R-value and airsealing worse) or to be declared toxic waste in 2050.
I was at a little toast for a colleague yesterday, and the young people wouldn't drink a sip of champagne from a plastic cup... microplastics!!
I think they both are problematic for retro insulation. Cellulose may not fill the cavity if there are any obstructions, it can settle if not done well and can absorb moisture. I did read about the water based stuff shrinking. They claim a lower % they people claim, not sure if the formula has changed or not. May never do anything. I don't live there and utility bills normally aren't that bad for an all electric house. We don't have gas as an option even if I wanted to go that route. The heat pump lost some temp over night with it -13F out, dropped to 62.5 during a defrost cycle. Still not bad. She doesn't seem to care about a secondary heat source but I could do propane or pellet stove in one of the existing chimney's.
The thermal bridging is a moot point as there is nothing I'm willing to do about it.
Retrofoam for example claims R4.6 per inch and these are true 4" studs. The siding appears to have a tar paper moisture barrier then some sort of cellulose based backing.
I looked at it with a thermal camera and was surprised the plaster and lath was colder where the studs were. I'd expect this in an insulated wall but not an uninsulated one.
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I don't have an explanation for the cold studs, unless there some (perhaps very degraded) insulation in there.
Anyway, with bridging by the studs, the assembly R-value is unlikely to be above 10 or so with foam or densepak IMO.
When I remodeled an old house that had a cellulose insulation blow in the walls done in the late 1970s I was shocked to find how good the cellulose retrofit was - there was no settling and every void was filled. I felt bad having to take it all out. A good, reputable contractor can do a great job with cellulose retrofits and the cost is very low.
