Im no HVAC expert but I think your air source is your return air duct inside your home. Sure, you'll get some outside air from opening doors etc.. but most should go through the return air duct

 

I work for a home builder in Austin. I can with out a doubt tell you that the foam insulation is WAY more energy efficient. This past december I had a house that was sheetrocked with no exterior doors installed yet. That morning it was freezing and there was a bottle of water frozen at 8am. Went back into the home around 4pm when it was 70ish and the bottle was still frozen. I donr know specifically the R value difference but its alot.

Foam houses due have a relatively higher humidity level. And it is very important to have fresh air. I am assuming since your house is almost new that your ac system has an fresh air handler on it. If it does then just the fresh air handler on and you should be good.



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Spray foam will seal your house almost as tight as a drum. Well worth the investment on a new build. Many moons ago when I worked at HP as a summer helper they had a spray foam system to seal components for shipping. Basically spray foam and plastic. Initially, the issue was the use of formaldehyde and the concern of off-gassing. I think the install is different now so that may no longer be an issue.

 

The A/C in a house doesn't bring in air from the outside. (A car's will, but not a house.) It collects heat from the inside, and ships it outside to be released - bit it uses the refrigerant to transfer heat, not air. In fact, one of the things about a spray-foamed house is that there isn't any fresh air exchange to speak of.

My house is like living in a giant Yeti cooler. When the electricity goes off, the inside temperature stays within a degree or two for a long, long time. Especially if we don't open the doors much. We also have a whole house dehumidifier. The combination works really well.

We have Low-E windows, but it is still easy to tell that the windows transmit a LOT more heat than the walls. The spray foam really does what they say it does.

 

I think foam sprayed houses in fact have to have a fresh air intake from outside to bring in new air because they are so tight. I think that's what the OP is referring to.

 

Spray foam will seal your house almost as tight as a drum.

Except for the need to bring in outside air (ERV) which is especially important if you have gas appliances.

 

It's rare for a home AC to have a fresh air intake. Humidity comes in from opened doors & windows, from your body to a minor degree and, in older homes, infiltration around windows or other "cracks" in the envelope. My biggest issue with spray foam is you can't really ever do any post construction work in the exterior walls like pull new wiring. Small price to pay, but if you plan to keep the house for a long time, it will eventually become an issue.

Spray foam has a better R value than batts, no question. As said above, the humidity is drawn out of the air at the coils and runs out through the condensate drain line. In more efficient houses, a system can work hard to remove the humidity and the by-product is it may cool the air more than you want. This is an issue a T-stat with a humidistat.

You might try raising the RH setting 10% and see what happens

 

In my home, the living area and the attic above the living area are foam sealed. The garage and attic over garage are not. The floor of the attic area over the living space has no insulation. That foam is under the roof instead.



I don't think there is a fresh air intake. Wouldn't it be obvious? And wouldn't it require an air filter?


My home isn't large, but I darn sure keep it cool in the summer. My electric bill here is half or less than my previous home of same size.

 

My house is foamed and has a devise to regulate % of outside air being pulled in ... sometimes a house can be too sealed up and C01 builds up to unpleasant levels ...
.

 

Wife and I have been shopping home builders and came across this in the Tilson videos you can find on line.

Tilson hooks a dehumidifier up along with the air conditioning unit and drains it right along with the unit. They have a formula they go over that takes in the size of the room, ceiling height and such and that dictates how many times an hour they need air turn over. Seemed to be way more sophisticated than our first house.

They are short videos explaining the building process and why they do certain things. Videos are all about 10 or 15 minutes long. Might be worth watching.

 

Design Tech homes used to advertise the outside air intake. I don't recall if they had a dehumidifier included. The concern at the time was being in a sealed house with all the off gassing chemicals from furniture, paint, etc.
I would have to put a sharp pencil to foam regarding any benefits vs. costs. Good old fiberglass and a leaky house has worked for me.

 

I have sprayed foam and am very pleased with the result. The attic is sealed and some hvac air is bled into the attic. The temp is only a few degrees different from the rest of the house. My wife uses the attic as a storage room and is comfortable there any time of year. No problem with humidity, there is a dehumidifier in the hvac system. Garages are also foamed and the temp is comfortable year round.

 

I sold insulation for several years (batts, cellulose, and foam). The R-value of foam is actually the same as batts. However, since you are sealing the house the foam is a much more efficient product. Also, if you use foam insulation on the roof, you are now putting the air conditioner equipment and ducts in a much cooler attic. Therefore they become more efficient as well.

I can't speak for all HVAC units but mine has a fresh air intake. I think it's the norm for foam houses now so you dont get a "sick house". A sick house happens by not having enough air exchanged daily in your house. Opening doors, leaking windows, etc may not be enough to cover the needed exchange. Therefore they put the fresh air intake to compensate. I don't recall all the health issues that can arise from a "sick house" but it's not good.

As stated above if the HVAC is oversized it won't run long enough to dehumidify the air properly. Mine does this and I have issues with condensation around some of my windows. I've been thinking about the whole home dehumidifier as well.

I haven't sold insulation since 2009, so some things may have changed.

***oh and I just remembered, the foam we sold for residential houses is open celled. Commercial used closed celled which I think did have a little higher R-value than batts.

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My 2800 sq ft house with high ceilings is very efficient with the spray foam. Highest electric bill I've ever has was $170 last August during the heat wave. AC doesn't run very long at all even in that heat.

 

This is more in line with what I was expecting. I saw up to $270 last year. Previouse house was built in 1986,same sq footage but lower ceilings...was in line with monthly bill amount (~$270 highest bill). I know there are many more factoring that can be used than just a sq, footage, but was extepting to be substantially lower with spray foam. My AC is not oversized, will run majority of the day in hot humid months. Not sure if I can remember it NOT running in daytime during last August. Has no problem getting to setpoint for temp, but runs more trying to reduce relative humidity. So, usual setpoint is 78° during day, it's keeping temp about 73/74, I'm thinking due to not being below RH setpoint.. I beleive the RH reading on thermostat is off by 8-10%. I plan to change that setting to 70% to see how it affects the system run time, while still monitoring RH on a separate hydrometer. (Budget friendly rocommendations??)

Pretty sure I'm down to 3 simple choices..
1) raise RH setpoint to 70% and monitor RH with seperate device

2) add hole home dehumidifier

3) possibly check in to different thermostat.

May do nothing and chalk it up to not enough research before paying much more upfront for spray foam upcharge. At this point, I can't say I'd recommend it to a friend.

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I'm curious about spray foam houses. Do they typically install a AC with a variable speed compressor?

 

There are more ways to seal a house now besides spray foam insulation. I spray foamed my house that I finished in Mar2019 and if I were to redo it again I would have put the money into a different air sealing method. I did open cell spray foam which has an r value around 3.5 per inch. Closed cell spray foam has a r value of 7 per inch but it also costs twice as much.

The company Huber manufactures an engineered sheathing that has an impregnated weather barrier. Once installed you tape the seams and it creates a very tight envelope. You don’t not have to install a wrapped weather barrier on this product. A lot of high end builders are using this method now on homes.



Yes I have a foamed house with a 5 stage system.

 

Like many have said dehumidifier, I have had a portable one since living on the island during Rita. Sears special still runs but makes some noises and I’m sure never ones are more efficient. 😂

We have a fresh air intake, I close mine during this time of year, reopen during winter in the cooler dry mornings.

The house are 2X6 walls, get some of the same results as far as electricity cost, but I like the idea of a foam sprayed (completely sealed home) for the next one.

 

I've built homes for over 40 years. Was a contractor for 25. If your house is to tight you chimney won't draw. Had one man get mad at me because he had open a window a little for his fireplace to draw. No air in no air out. Biggest problem I found with outside air coming into fireplace it also comes into the house, smoke with it. To me if a home is to tight, like said earlier, sickness. Where can it go? Seems like now when someone got sick in my home so did everyone. These new high efficient are designed to run long on way less amps to take the moisture out of the air in your home. So you don't want to put an over size unit in, because it won't run enough. This was all from my a/c man. Most A/Cs now, if not all, are designed to bring in outside air which I feel is great. Energy efficiency is big thing in a home but there is more than just insulation. How many windows are on the north and west side of the house. How energy efficient are the windows? How much overhang do you have shading your windows? How high is your ridge of the roof away from the ceiling? Door efficiency? Check with your power company, they are always have incentives and rebates for building an energy efficient house. Mine wrote me a $2400.00 check, not deducting it off the bill. Also look into how long it takes you to get a return on your extra investments. For example my A/C was double what a conventional unit but according to the efficiency level in 4.1 years I would save on my electric to cover the costs on the extra payment. Now 26 years later what am I saving. This is just a few thing you can do to make your house energy efficient. The way I looked at it was to pay for it while I was young and could, and enjoy it now later while I'm older and not have to work as hard.

 

My fireplace doesn’t draw any air from the house. It’s a sealed unit with a vent stack that is dual chambered to draw in atmospheric air and exhaust combusted air out. Heat radiates through the glass. More for looks than function.

 

Hello.

we live in an OLD home, built in 1905. it's sitting on a crawl space. currently, the only insulation underneath is the panels of rolled insulation, but it is taking on moisture and falling.

we have had an energy audit, and the company is recommending a spray foam insulation (in combination w/ putting down plastic on the floor of the crawlspace), to be applied to the "ceiling" of the crawlspace.

MY CONCERN: this spray foam IS chemicals. the company says they are using the best, least toxic product they can find insulation dc insulation dc, and that off-gassing is only a few days. online i've read that some people have had to move out b/c of fumes that last months.

so, i'm very worried that this is our only viable option (we NEED some insulation there, and what we have now is only inviting mold), but it is not good at all.

any experience/wisdom/ideas?

thank you!

 

Hello.

we live in an OLD home, built in 1905. it's sitting on a crawl space. currently, the only insulation underneath is the panels of rolled insulation, but it is taking on moisture and falling.

we have had an energy audit, and the company is recommending a spray foam insulation (in combination w/ putting down plastic on the floor of the crawlspace), to be applied to the "ceiling" of the crawlspace.

MY CONCERN: this spray foam IS chemicals. the company says they are using the best, least toxic product they can find, and that off-gassing is only a few days. online i've read that some people have had to move out b/c of fumes that last months.

so, i'm very worried that this is our only viable option (we NEED some insulation there, and what we have now is only inviting mold), but it is not good at all.

any experience/wisdom/ideas?

thank you!

We insulated our 1904 house with foam insulation and have had no issue with off-gassing.

 

Since we are on the subject of insulation, I would like to spray the other kind in, the kind that I rent the machine and buy the fluff. Question is, do I spray it down in my eves? When they "built" the house, they put some channels between the roof joist to allow air to be drawn in from the eves. I suppose I need to either remove them, or re-attach them to the roof decking and spray on.

 

Since we are on the subject of insulation, I would like to spray the other kind in, the kind that I rent the machine and buy the fluff. Question is, do I spray it down in my eves? When they "built" the house, they put some channels between the roof joist to allow air to be drawn in from the eves. I suppose I need to either remove them, or re-attach them to the roof decking and spray on.

No, you do not want to block the insulation baffles. The only time you would want to do that is if the insulation is being applied to the bottom of the roof deck. With the insulation type you are talking about...recycled paper...be sure and spray more than what you need as it will settle more than most.

 

I am no pro , but In my research and my neighbors research and talking with a engineer from what I understand that if your home is engineered for spray insulation then you can use it if your home is not engineered for it then more damage can occur overtime. That’s what I was told. I don’t know if it’s right or wrong.


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Slow Rolling
Your buttoned up better than most submarines over there. Your not losing much efficiency letting in the fresh air.
You 100% need that. Since your home is new its not like others which have a little spray foam in the attic.
The new TDLR energy efficiency guide lines follow the latest gov energy codes. Comcheck is the gov software used for compliance. This sucks to most of us industrial people $$.....
If you see humidity on the Tstat, odds are you already have a dehumidifier. Yes, the HVAC does pull humidity from the air.
Not going into how all that works........
Your sitting about 250% more efficient than the rest of us. Monitor the humidity and see if it runs high. Might need a humidistat? More than likely not. If the unit is sized correctly and not too large, it will pull the humidity from the inside air.
It is sized to handle the incoming fresh air.
Sit back and enjoy the cost savings!!!
I have been building industrial offshore and on shore electrical buildings for more than 25yrs.
Hvac is a big part of the overall project.

JUST GOT DRUG INTO AN OLD 2020 POST - Don't you hate that