Experiences installing Central A/C in 3 story house (rentals, heat pump)

[ctkalino]

We are looking to install A/C in our 3-story, 3,000 square foot house. It's 110 years old, so no ducts (we have radiator heat). We have obtained some quotes for different options, including traditional ducted, high-velocity, and mini-split system. We have a good layout for retrofitting in general and room for traditional ducts. We are leaning toward doing only the top two floors now, either with traditional ducts or high-velocity, and seeing where that gets us. Down the road, we would consider installing a mini-split on the first floor, both to help cool it and to help warm it in the winter because currently our first floor is freezing and our top two floors are boiling in the winter.

My question is: does anyone have experience with installing A/C on floors 2 and 3 only of a 3-story house similar to ours in size, and how did it work? Was the first floor still very warm?

Also interested in opinions on high-velocity versus traditional ducts for the top two floors.

Thanks.

[TechCom]

Avoiding the one floor isn't gonna save you hardly anything. Upstairs can be completely cold and the downstairs will be hot.

[Der Schwabe]

I would also be interested in heading some experiences, as we're thinking of doing the same thing. May I ask what the quotes were for high velocity vs regular and just upstairs vs whole house?

[Bong477]

We have a 4000'ish square foot house, 110 years old. When we bought it had ducts and gas heat + ac on first two floors, nothing on third. We wanted to finish the third for some guest rooms and a play room. There used to be some heaters up there but had been removed by prior owner. Looked into a few options, figured in my head that a mini split would be best for the third floor but in practice ended up being not very practical and very expensive to install. Ended up with a heat pump + traditional ducts which we bulkheaded in. Cost around 10k for hvac (could have cut some corners and got it down around 8) another 500 to enclose it. The heat pump works well in moderately cold weather, but is expensive to run during very cold days (like single digits or lower). Mini splits tend to be the same with very cold temps, there are some models you can get that do better in colder temps but cost more. It doesn't get insanely cold even with no heat, but is uncomfortable. We don't use it every day so the solution is pretty good for us. Its nice to have the third floor zoned separately from the areas we use every single day.

My opinion would be not to skimp on the first floor, but if you spend a lot of time there and use 2nd and 3rd floors daily, a second zoned system for the first floor would be reasonable. Your problems with the cold might be more of an insulation issue or adjusting your radiators?

[gg]

I ended up with high velocity because I have very little room for conventional ducts. I love my high velocity, but you can hear a bit of wind noise. It doesn't bother me. The humidity is lower with high velocity than conventional, so you don't need to keep it as cool. At 74, it feels pretty darn cold in my home because the humidity is so low. Conventional is quiet and usually cheaper. For some reason our region loves conventional, but if you can find someone that does HV, that is a good option. I also looked at splits, but they are pretty ugly! There is crap on the outside and inside of the home and I don't think I would like that long term. They work well, but I think I wouldn't do a split unless it was a bunch of rentals or a cheaper home. There are two HV systems and I think both are good.

Good luck. I love A/C! LOVE!

[scrapp]

Originally Posted by ctkalino

Also interested in opinions on high-velocity versus traditional ducts for the top two floors.

Thanks.

We have high-velocity on our second floor. The blower unit is in the attic above the 3rd floor and the high-velocity ducts run from the attic to the second floor through the knee walls on the 3rd floor. The high-velocity system does a great job cooling and removing the humidity. The newer high-velocity units have variable speed blowers that spin the fan up to speed gradually rather than all at once (so the start up noise is smoother). The high-velocity systems are more expensive (and if you want to use it for heating too, then you have to pair it with a heat pump or hot water).

[SorryIMovedBack]

currently our first floor is freezing and our top two floors are boiling in the winter.

Did you already balance the radiators and bleed the air out? That made a huge difference in the one house I lived in that had steam heat. I had a HVAC engineer friend do it but there is information on the Internet.

[ctkalino]

Originally Posted by Der Schwabe

I would also be interested in heading some experiences, as we're thinking of doing the same thing. May I ask what the quotes were for high velocity vs regular and just upstairs vs whole house?

We obtained estimates for various options from two companies (so far). One only does traditional ducts. The other specializes in high velocity and mini-split systems.

High velocity top two floors: $11,500. They then gave us an estimate for cooling the first floor with a separate traditional unit, to be installed in the basement. That was an additional $8,000. Using a mini-split system on the first floor (with units in three rooms, which is probably excessive) was quoted at $10-11K.
Traditional ducts top two floors: $14,000ish. To add the first floor it would be closer to $19,000 total.

Turns out our neighbors did only their second and third floors, which I had somehow forgotten. They used traditional ducts, and it cost them ~$8-9K. They said that was by far the lowest bid they received though, and others were up to $5K higher. They also said they are completely satisfied with having only done the top two floors and their first floor stays very cool.

So, we're now leaning heavily toward doing just the top two floors.

[ctkalino]

Originally Posted by SorryIMovedBack

Did you already balance the radiators and bleed the air out? That made a huge difference in the one house I lived in that had steam heat. I had a HVAC engineer friend do it but there is information on the Internet.

Good suggestion - we definitely need to do this.

[Doofy-88]

I'm not an HVAC guy --- but did you look into zone control for your A/C needs?

Multi-story homes are notorious for having wide variation in temperature during summer months -- VERY hot in the upper floor while thermostat is on ground floor keeping things cool. With zone control, you can have cool air being ducted only to where it's needed (such as a hot upstairs bedroom).

That way, you arent wasting 100's of dollars this summer trying to keep the entire 3 stories cool, only where you want it to be cool. Modern climate control systems are very effective and energy efficient, and you can fine tune this system easily on your PC and WiFi network.

Zone control is what you need, my friend

https://www.youtube.com/watch?v=7ebkrRS4C9A