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I have an unfinished basement in Upstate NY in a large old house that helps in keeping the house cool in the summer. Would insulating it limit the cooling effect in summer?

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Wait... You want your house to be warmer in the summer? – Tester101 Sep 6 '13 at 16:35
I don't see where he said he wanted to "limit the cooling effect in summer". – Philip Ngai Sep 6 '13 at 18:13
FWIW, in MN, where summers are also brutally hot and humid, while our insulated basement was warmer than when it was unfinished, it was still cool and comfortable as well as a lot less humid. – DA01 Jan 21 '15 at 16:25

Yes, insulating the unfinished basement would limit the cooling effect in summer and increase your cost of air conditioning. On the other hand, the uninsulated basement cools your house in the winter. The question is, which one would be less expensive if you want to keep your house comfortable in both summer and winter?

The only way of avoiding the tradeoff is likely impractical, you would need to build in an extensive air plenum behind the insulation which would allow you to extract cooling when desired by blowing air through the plenum. This is actually a form of geothermal energy.

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That cooling plenum idea is so bizarre.. I thought the same thing.. It would need to have some condensation recovery built in, perhaps sloping the plenum and draining to the sump, or using a condensate pump. – HerrBag Sep 6 '13 at 17:45
It's unconventional but not unprecedented! Agree about the need to deal with condensation. campmackinaw.com/earth_tube_cooling_heating.htm – Philip Ngai Sep 6 '13 at 18:12
Insulation slows heat transfer, it does not stop it. I live in a similar climate, my basement is lightly insulated and stays plenty cool in the summer despite on the hottest days blowing air up the stairway, drawing in hot outside air. Enough of that heat still leaks into the ground to keep the basement cool enough that one needs a sweater to spend any time down there even on the hottest days. In such climates, limiting heat loss is more important than increased cooling load which I expect to be negligible. (I have no active cooling at all) – bcworkz Sep 6 '13 at 20:32

It may seem counter-intuitive to think insulating a basement will prevent it from being cool in the summer, but this has truly helped me keep my home cool during the hot months. The insulation keeps the warm air in, and the hot air out. It has definitely helped me stay cool in the summer and warm in the winter!

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First the term "basement" in the technical term is supposed to be used for a floor that is completely below ground level. Almost nothing in the US is built like this for residential. So I will use the term basement to mean many things but not for what it is technically supposed to be used for.

Working with a local company doing energy audits on basements and finishing more basements than I can remember to count I have taken a few things away with me. There are a lot of factors that should go into the design of your insulation. So to answer your question in its most basic form - yes adding insulation will make your basement warmer in the summer for sure.

List of factors:

  1. What is the variance of temperatures in your house during the most extreme weather (hot and cold). You are in NY so you can have 100F - -20F. So given your thermostat is set at 72F all year long what is your basement floor at when it is 100 or -20. There are specific remedies depending on the variance. With lower variances you need little to no insulation in temperate climate.

    Reasons for variations:

    • Type of basement walls.
    • Condition of basement walls
    • Thickness of walls and slab
    • how many windows
    • what percentage of the basement is above grade
    • others
  2. Climate - If I am doing a house in Toronto it is getting a ton of insulation. In Texas (yes there are basements in northern Texas) probably none. In between it gets tougher to say.

  3. How will the basement be finished? If you are drywalling a basement, then your basement and house will be noticeably warmer with drywall by itself. That factors in.

  4. What is the budget? In colder climates you would want insulation on the outside of the house. Spray foam is probably the most effective and leads to the least amount of mold issues. But is there budget for this? No use offering a solution that will not be used.

What do I suggest for a very temperate climate:

  1. Any part of the basement that is not "under ground level" gets insulation for sure. I offer three choices: Spray foam, rigid panels, or rock wool. So if you have a walkout - that whole wall is done.

  2. Keep insulating until you have diminishing returns. This is really hard to figure out unless you know an area well or it is the coldest part of the year. So for instance if I do a house in Kansas City, I would go about 1-2 feet below ground level. I just did this at a friend's house using rock wool. The inspector was impress too because he knew that the winters are short and that doing the whole wall would impact the summer temps.

  3. I hate putting insulation on the bottom 3-4 feet of a basement. First I find it is of little value unless you are in a very cold climate. Second I want a large air gap behind my drywall. Give moisture room to fall and evaporate.

  4. The main concern with insulating in any climate is to keep from having a huge temperature variance. That means in NY I would make sure that all of the edges of that basement were overinsulated in the the joist/crawlspace areas. I would be stuffing every nook with rock wool going 1-2 feet deep if I need. I would probably run it another 2-3 feet below ground level too. On a cold cold winter day I want the temperature in one of the upper corners of my basement (should be the coldest point) to be the same as the center of the basement floor.

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The common usage of basement is 'that room under the house where the walls are the foundation'. That usage seems to trump any technical definition. – DA01 Jan 21 '15 at 16:27

I did my entire basement with spray foam a couple of years ago. The basement is still cool in the summer, but not as cool. But it is now usable in the winter.

One assumption we might make is that fossil fuel costs will escalate more than electricity costs. If this is true, savings in winter heating costs will offset the additional air conditioning costs. And fundamentally, this is the question. How can I maximize comfort for the lowest total cost?

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I think it depends on the climate. This is information I got from construction contractors on this question.I found this question while looking to write a similar one on home cooling system that is energy efficient or non energy use.

Environment Outside: 78-86 degrees and breezy in the summer. 55-60 in winter. Environment Inside house: with the heat at 80 degrees and muggy in house.

In the past (prior 2005), 3bd houses or likeness were homes built due to the need of modern homes not plantation tin roof and wood. Old plantation homes were and are cooler having single wall, high ceiling and tin roofs sitting about 3-5 feet stilted of the ground ( flood zones a single level sitting at 3rd floor stilts.) *this doesn't include custom beach front property or Japanese style homes with all wind open sliding door walls.

In the past prior to 2005, construction was suggested to leave out ceiling insulation in the modern dry wall homes. Not just to cut cost. It was because...

-Insulation keeps the roof cool cold temp out during the nights that drop to 55 degrees due to the ocean and mountain breeze (both 1min walk to 30 min drive away depending where you live.) The cooling is something we want, and I would rather sleep in my tent with the skylight than lose that. [This opt out option was the best idea for our hurricane rebuilt home- our beachfront blocked by a large 3 story building as wide as 4 homes without community approval. Community not educated that they could deny the 1999 commercial building. I was 13 building my home after 1992 Hurricane. ]

-Insulation keeps hot air in, and the breeze out. The temp exchange is slow. More window treatments would be needed for sunlight and letting in the breeze. [ Even with insulation your house will still be hot, it doesnt stop the heat. There are other options.- Myself and K. Sakai construction worker 2014]

-Insulation keeps hot air out, but that would also happen in the summer everyday sun in summer and winter. Here we find one positive thing... insulation slows the heat from coming in. It will spread around the roof till it finds a leak. [Schoenhardt -prior AZ roofer/current:HI weatherman 2013]

on the average temperature range of both seasons Ho'oilo (winter Sept-jan) and Kauwela (summer Feb-aug). Both season ends in rain storms, through out the year " random" down pours due to humidity conditions of having the mountains so close to the ocean ( a day drops 20 degrees nearing the storm months).

Temporary alternative to this solution: fan, AC and humidity appliances. The same I use in HI , i used in TX and CA, USA. But there's more...

Possible answers with the help of our environmental friendly engineers... DIY My initial question was does anyone have the best quality and fair price to compare the solutions with?(see below)

-Step 1 :Hurricane/Severe weather energy and cost efficiency DIY Solar power roof vent fans . $67-$600. They push out hot and cold air from ceiling or attics. Naturally a vent doesn't need energy, for heat rises; the cold air can't get into your roof. Cold weather cools your roof.Cover your fan solar in winter if in icy conditions i.e. my TX and CA weather at my families homes I lived with and did construction for free rent ( Eventually this ocean minded surfer in 103* inland and drought -I didnt use any energy on fans or Ac...because of the additional below)

Example: http://www.homedepot.com/p/Active-Ventilation-5-Watt-Solar-Powered-Exhaust-Attic-Fan-RBSF-8-WT/204203001?cm_mmc=shopping--googleads--pla-_-204203001&ci_sku=204203001&ci_gpa=pla&ci_src=17588969&gclid=CK-864fBkcACFStgMgod2XcALw

-Step 2: Tubular skylights. $222 It cut the cost of heat emited into the home. There was no LED other than my camera and computers that already emited the same heat as outdoors. They can provide heat due to the sun reflection into the home. No other energy used for it to be on during the day for extra lighting from facing walls. Example: solatube, velux , odl

or Reg Window skylight $1200. It can catch the wind from raising the window pane and let light in. Keeping the home cool. In winter cover it before the snow.

-Step 3:UV light reflecting paint/Roofing coating $80 5 gallon. Goes right over shingles.(This is followed by Step 4 sequentially in close time frame)You paint as if you are painting your house- one area and direction to the other. dont over coat, let each layer dry. Use 2 ladders to get on and off at the opposing corner. Example :Henry's Brand

-Step 4: Silicone Roofing Paint $250 5 gallon. You can layer as needed. Please read and watch instructions before painting your roof for the cost and safety!The adversity of weather will make your roof slippery as it dries. The paint dries in hours, so the best days to do it are those overcast days or mornings where it's cool, and then becomes hot when sun shines through.The silicone acts not just as reflective paint, but as a reflective heat sealer. Paint similar to Step 3. Example: Cheapest and quick Greco. Expensive up to $600 that is just one coat up to 20-50 years warranty.

When you have enough... Change your windows or seal the corners better. If using fans or AC in one area close all windows and doors; or the door to a room you want some of it leading into.

Full Ceiling Insulation costs will be close to over the price I spend on the above cooling/heating system. (Based on Homedepot Budget with no other comparison)

Tip: Do your landlord a favor and let them know, do your comparison research. You can trade for rent. I would so love that! Now to find the comparison supply measurement, quality and price for myself to so at a residential consumer cost...or as construction companies if they can share the whole price.

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Olo, I'm a neighbor of yours (Vermont), so I know exactly what you're shooting for.

Insulate the OUTSIDE of the basement, not the inside.


Insulating the outside leaves all that basement-wall mass as part of your place's thermal mass, lending thermal inertia, stabilizing your interior temperature. I allows the walls to attempt to reach the "earth normal" (around 45*F) temperature that comes up from the basement floor instead of January's -30*F or July's 100*F. In winter, it's a LOT easier to heat those walls from 45*F to room temperature than it is to heat them from -30*F to room temperature... and in summer, their preferred 45*F will be a welcome relief from the heat.

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