What kind of heating/cooling system do i need in a house with spray foam insulation? Two story on a crawlspace, with 2,200 sq ft downstairs and 1,300 upstairs. I know I need two units, and I ‘think’ I need a 3 ton unit downstairs and either a 1.5 or 2 ton unit upstairs. I’ve been told I need two stage condensers, but have also read online that that’s wrong. Also, no gas so all electric units. I don’t really know for sure what specifics I need, but do know that a spray foamed house requires more than the average install. I’d appreciate any good advice from folks who really know what they’re talking about, cause I really can’t afford to get this wrong.

Not the batey Bros, but really need to get a load Calc ran on the house first. That way u can get the size exactly right instead of guessing

There are too many variables to simply answer that question on this forum. As stated, you need load calc. If it's new construction the state of Alabama requires DET testing. If you've had DET testing and passed it, then you don't necessarily have to have two units. That home would require far smaller systems than the traditional homes built before 2012 (I think it's 2012 when DET testing was adopted). Old knowledge simply won't apply to new construction.

Spray foam can/will affect a house on a load calculation. So, as others mentioned, if this is a new build, I would ask my contractor to have a load calc performed to be sure. Going off of “old Rule of thumb” numbers, without spray foam, you are close on tonnage, but spray foam could/will lessen that load.

As far as equipment goes- I always recommend variable speed inverter driven systems on spray foam, two stage can get you by, but to be done right, I like Inverter. With that I also like to have a fresh air systems integrated- ERV/HRV. These houses can be built so tight, that you’ll want fresh air.

Additional stand alone Dehumidifiers may be needed in some applications when two stage equipment is used and unable to control humidity levels. It would definitely be recommended if someone tried to use single stage equipment. And with all of that said, sometimes its not a bad idea to have one integrated into the duct system regardless of what system you have on a spray foam house.

I like spray foam homes, but once I explain to potential home builders/homeowners that they need 70k+ worth of HVAC equipment, and their budget was 10k, they opt for standard construction and base level HVAC options. No one wants to skimp on granite countertops, flooring and fixtures, but they’ll slap the cheapest option in for the mechanical systems. Beats all I’ve ever seen.

Thanks for the feedback. Definitely helped in my conversation with my A/C guy.

Just curious, what does the spray foam cost per sq ft?

My place in Evergreen is spray foamed and just have a standard unit with no special equipment. It's a single story slab. Seems to be just fine to me, what kind of issues should I be having or expect to have considering I don't have $70k worth of HVAC equipment?

That's what I wondering why you need 70K worth of AC equipment if use spray foam. Why bother if you gotta drop that kind of money?

Well, I guess I’m referring to the whole scope of things for a larger home and not a small slab house. 3 Ton custom built Duct System, 2 Ton custom built Duct System, 3 Ton Split Inverter system, 2 Ton Split Inverter System, ERV/HRV Fresh air for either system, advanced air filtration/purification, dehumidifiers for either system. Wiring, controls, piping and etc. The above scenario may not be in the 70k range, but on some of the houses around here that I’ve seen, 70k may be normal and may not even touch what all is needed if it were to be done “right”.

We’ll use common sense on this one and say on a single story slab house, the expected costs would be way less than a custom built home, or home that is 2-3X or more of that size.

But to answer the question, the most common issues I see out of spray foam houses is over-sized HVAC systems. They run long enough to remove sensible heat, but never touch the latent heat and leave humid situation in a house. It’s definitely not an uncommon situation. A hundred plus high end houses in a Huntsville area subdivision dealt with this years back when they went all spray foam and had oversized AC units. If you aren’t dealing with issues, that’s good, Not everyone with spray foam will.

Another common issue I’ve seen is homes off-gassing all the chemicals from everything used during construction or brought into the home. An air tight home can’t breathe and in turn just circulates the chemicals released from everything in your home. That’s where fresh air and air cleaners/purifiers come in. Headaches, nausea, sickness and etc are the results when this is at a high enough level.

Most HVAC contractors, especially in new construction are focused on simply providing hot or cold air at the cheapest price the builder can get them to and that’s fine. We can control the cleanliness of that air, the humidity of that air, the volume of that air in which it moves and circulates and bring in enough treated fresh air to keep everything happy and healthy. It’s a premium product, at a premium price. Not for everyone. Most people building a home don’t care about the mechanical systems until it becomes a problem, they would rather spend that money on something flashy that their wife can show off to the neighbors wife- counters-cabinets-fixtures and etc. Mechanical systems aren’t sexy enough to most people to justify the money.

With all of that said. We don’t target new construction and I doubt we ever will.

that makes sense when you put it into context. I can see were the bigger homes can get into the commercial side of HVAC

You talkin' bout me?

You had a well thought out system.

I’ve saw multi million dollar homes that I am ashamed of the lack of quality or thought that went into their HVAC, plumbing or electrical systems.

Just this week I was in about a fairly new enough $1.5mil house and boy did they have a jumbled mess in terms of HVAC. Counters and cabinets were to die for, though.

I heard of a house on Ono Island that had to be torn down because the spray foam insulation hid the fact that formosan termites ate the walls completely up. That alone is a no go for me on spray foam.

Regular insulation and drywall can also obscure it. Spray foam isn't any better or worse for termite. However, it can obscure leaks, staining and such for a much longer timeframe, allowing damage to advance much further before it reveals itself.

This.

Just remember that there are 2 types of spray foam used in houses which are open cell and closed cell. Closed cell you better make sure you have everything sized for the house with a way to get fresh air in and humidity out. open cell is more forgiving.

So, my house is 3000’ on crawl space built 25 years ago, installed fiberglass but over the years it has been falling down the question redo with fiberglass or spray insulation?

I personally like spray foam. The R value is much higher, and it quick to install. I just had it added to my new build, along with rock wool on the interior walls in the house for sound. It is amazing how quiet the house is now. I could not hear my wife on the tractor bush hogging up close to the house. My current house has it, and my utility bill stays around 250 a month including trash and water.

How much is spray foam per sq ft?

Mine that was sprayed last week was 6K for the exterior walls with 9ft ceilings, and the roof deck, and rock wool in the interior walls. That was on a house that is 30 by 50 and a 6/12 roof rafter.