Guido: I’ve got a six year old lower-end rental house, and my tenants are complaining about excessive air conditioning bills. I had a contractor go in to assess the situation. Having used a FLIR,“ forward-looking infrared camera ,“ there’s a ten to fifteen degree temperature difference between the first and the second floors. We’re losing so much air conditioning out of that place on the second floor. It isn’t a high-end house, but still, what can we do?

Jared: Ventilation is key. That’s what allows the hot air out of the attic space. The air conditioning could be a culprit. You need to check around all the joints of the duct work to make sure that it’s sealed properly and there is no air escaping. Insulation is really important ,“ making sure that everything is insulated properly. The way that houses are typically built is that you allow the hot air to penetrate the envelope of the property into the attic. We find an average second story attic is between 150 and 170 degrees. That’s a lot of hot air that’s sitting in the attic, and that air can come in and allow the cool air to escape.

I would also check the HVAC system, just to make sure that it’s sized properly, that the ducts are sized properly, and again, that the duct work doesn’t have any breaks in it. Then the next thing I would look at is the insulation and make sure it’s done well. Have you considered installing a radiant barrier or thermal barrier to stop some of the hot air from getting inside the attic?

Guido: That was the suggestion.

Jared: I want to discuss this whole process with you, because it is not just your house, Guido, with this problem; lots of people in Florida are dealing with this same issue.

Guido didn’t stay on the line during the break, but I want to continue on with this issue. One of the questions I would have asked him is whether or not he had a second air conditioning unit for the upstairs. It is common in not so expensive homes to only have one unit controlling the downstairs and upstairs. It’s a good idea to have two separate units; that way they’re running independently from one another. It’s naturally going to be hotter upstairs, as hot air rises, so it’s common that the second story would be warmer than the first story; with two units, then the second one can turn on sooner and balance the air between the two.

Josh: There’s no happy medium. I’ve talked to AC guys about this before, and if you just put a second thermostat upstairs thinking that’s going to cure it for you, it might ,“ if you like to be a polar bear downstairs. The air upstairs might be 78, what you set it at, but the downstairs is going to be 60 because it’s working so hard to keep that upstairs cool. I know a lot of the big companies make these things called mini splits ,“ which are small versions of an air conditioning system with a small compressor ,“ that you could even bolt to the side of the house and hang outside of a window for those instances where you need that little extra kick of cool air.

Jared: We use the mini splits a lot when we do remodels. In fact I talked to two or three different people this week who are thinking about doing small additions on the back of their house. They’re closing in a patio, adding a patio or a master, and oftentimes, rather than replace their whole air conditioning system, we’ll add a mini split for that area. It’s usually just a couple grand to add it. It’s a great, inexpensive way to get air conditioning to a section of home that didn’t have it before.

In answering Guido’s question about the air conditioning, it might be something like that. It could be just the duct work; an issue where you don’t have enough returns in that area ,“ because no matter how much you push the cool air in, if there’s not some way to get the hot air out, then the air conditioning system wouldn’t work properly. It also could be a function of the insulation. Insulation is really key, and I’m seeing a lot of people changing their insulation system. In fact this is something that we’re doing in the project house.

We, just this week, sucked out all of the insulation that is in the attic, and we’re going to do a new spray foam insulation on the underside of the roof deck. What this type of insulation does is it actually stops the hot air from ever breaking the envelope of the home. I know that you have this in your house.

Josh: I do, and knowing what I know now about spray foam, there’s no other insulation I would recommend. You can go up into my attic at any time of the year. It’s probably, at the most, only five to six degrees warmer than the inside of my house. You can go up there anytime, get your Christmas ornaments or whatever you’re storing up there, and you don’t have to worry about coming out itchy. There’s not a speck of fiberglass insulation or blown newspaper anywhere in that attic, because you don’t need it. The soffits are sealed. The attic’s sealed, and the best analogy I can think of is a Styrofoam cooler. The entire roof is like if you flipped over a Styrofoam cooler, and the entire underside of the roof is coated with foam.

Jared: It is true. With a two-part foam insulation, your attic temperature is four to five degrees warmer than what the inside temperature is. So, let’s say that you keep your house at 75 degrees, could you imagine your attic only being 80 degrees?

Josh: That’s unbelievable.

Jared: Most attics are 130, 140 degrees. It’s crazy how hot they are!

Josh: Another thing is, if you have your cable guy or someone else up there, and then the next thing you know, you’re AC’s not working right. Check your attic; check your duct work. Because when those guys go up there ,“ they’re working in maybe 150 degree heat up there ,“ they’re not always careful of where they’re stepping. Obviously they don’t want to step through your sheet rock, puncture into your house, but if they step on a duct and just jar it loose, you actually might have your return sucking air in that’s 160 degrees. Or you could have a vent blowing out, basically chilling your attic. If you don’t have the foam, like I have, there’s really no way to keep that attic that temperature down, especially with the heat that comes in from the roof.

Jared: Thanks Guido for that call. If you want more information about the spray foam insulation ,“ or any type of insulation ,“ we do insulation at our business, Universal Roof and Contracting. We’re building and roofing contractors. Contact us, our phone number (407) 295-7403.

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