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Getting cool air from basement into the house

 
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I'm trying to find ways to make the house comfortable without burning fossil fuel.

In summer, my upstairs is sweltering while the basement is always a cool 65 degrees Fahrenheit. Is there a reasonable way to pump that colder air up to cool the higher floors? This would use some electricity, but much less than an air conditioner, because the air is already conditioned. My house doesn't have duct work, though, so I'm not seeing a good way to do it.

Just wondering if anyone has experience with this kind of thing.
 
pollinator
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I've never done it myself, so take this with a grain of salt, but I think you could do it without electricity at all. Look into earth tubes and passive cooling. Normally people do it with tubes set into the ground, as the name implies, but I would think a basement would work fine.

You could of course implement it with electricity to increase air flow, but it might be worth experimenting without it first. I'd be curious to hear the results from someone who's actually done it!
 
gardener
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I think I would run a loop of 3" flexible dryer duct across the nascent floor/walls.
I would use a bathroom fan to circulate the air,  with the end that was coming from the basement ending at the highest inhabited point in the house, and the intake at the lowest.

Attach it to a solar chimney for a no electricity option.
 
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Hi Joshua;  
You could try getting that cool basement air upstairs, but I'm afraid that it won't make much difference at all.
Do you live where it is hot and humid all summer?   If you do its a losing battle with out using A/C .
I grew up on the east coast.  All summer 98 degrees and 98% humidity... until late at night when it dropped to 88 degrees and 98% humidity.... No fan worked , to wet for swamp cooler. It was just xxxing hot! The basement was cooler but how long does a kid want to hang out in the cellar?
Dad refused to get A/C for years under the theory that they did not have them when he grew up.

If you are lucky enough to live where it is not humid and where you get cool night time temps even in the summer, then you have options.(like northern Montana)
We leave our house open all night to cool it off. Then at oh 8 AM or so we shut every door window and curtains all day.  It is very nice until late afternoon or early evening.
 
master pollinator
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Hi Joshua,

I don't hold out much hope for significant success but why not use a fan to move the air out of the basement into whatever upper room is readily available for a few days. Track the temp with a thermometer.  This should be enough of an experiment to see if it is worth further effort.
 
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Do you have a photo of the house?
You will reduce the heat upstairs with insulation on the ceiling and sisalation in the roof behind the cladding.
Also adding an air vent capable of removing hot air from the cavity will help a lot.
You can get thermostat operated ones which removes hot air when it builds up, the ordinary units are hopeless.
 
Joshua Frank
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John C Daley wrote:Do you have a photo of the house?




The first floor is a big rectangle divided into rooms (and a garage). The second floor is a smaller rectangle in the middle of that triangle under the roof. There are unused crawl spaces on the sides of the triangle, and an unused attic above the second floor.

There are louvers in the attic, so I'm wondering if fans up there blowing air out (and maybe airflow grates on the upstairs ceiling so heat can rise easily between the second floor and the attic) would help keep the upstairs cool. Has anyone done this?

 
John C Daley
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Photo helps a lot
I am as Aussie, so our homes are built differently, but I have studied the differences.
Sometimes I have found that the 'vents'  actually do not vent, they are there for appearances.

I imagine it would be difficult to add anything inside the upstairs ceilings?
But often the walls to upstairs are not insulated or not insulated well, that may be looked at.
What temperatures are you looking at?
My home in Bendigo Australia becomes uncomfortable with a room temperature of about38 celcius with a ceiling fan operating.

 
thomas rubino
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Common construction here, uninsulated  roof and an insulated ceiling.   Vents do work ... they are  just keeping the air in the attic from becoming to hot.
Would do nothing about circulation inside the house.
 
pollinator
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"There are louvers in the attic, so I'm wondering if fans up there blowing air out (and maybe airflow grates on the upstairs ceiling so heat can rise easily between the second floor and the attic) would help keep the upstairs cool. Has anyone done this?"

I have done something similar, and it works, using a scrounged high-volume furnace fan. And there are all sorts of high-volume attic ventilation devices at big box building stores for exactly that reason.

The attic fans are designed for cross-ventilation within the attic itself. For the level below, if you have cooler air outside at some point in the day, you could in theory create openings to the upper floor and draw cooler air in through open windows on the shade side. With many houses, insulation/vapour barriers/wiring etc. would make that a royal pain. You could also create the same cross-draft using just the windows themselves, blasting warm air out and drawing cool air in. With high volume flow, it works.

It becomes tricky if you're trying to draw basement air upwards, though. That means cycling in warmer, more humid air that will condense in the cooler basement. Potential mold/mildew traps there.

Before you start chopping holes, consider: If you don't have radon issues, perhaps the easiest and most energy efficient solution is to adapt: move yourself, and sleep downstairs.

My 2 cents.
 
pollinator
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I agree with the last post that drawing air from the basement means passing outdoor air through the basement. You'd have to open a basement window and suck air out the highest place possible in your house, which would likely have the undesired effect of bringing a ton of moisture into your basement (as the warm humid outside air loses heat, it would drop it's moisture on every cool surface of your basement.)

The strategy we've adopted at our house is to use awnings wherever the sun comes in the windows, especially the west side. We didn't want to install an attic fan, so we put a "suck fan" on a back room window that we turn on as soon as the outdoor temps get cooler than indoor, usually around 10pm. The fan draws cool night air through the house, and mid morning we shut off the fan and all the windows. With proper shading, the house stays cool without A/C until late afternoon/early evening and we only run the A/C a few hours a day.

I was frankly amazed at how well awnings work. When I covered the west window especially. Even the cheap sun-sail shade awnings help.  
 
John F Dean
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I don't see why inside air can't be recirculated without drawing outside air in.  A simple air return from the upper lever to the basement would achieve that.
 
Douglas Alpenstock
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John F Dean wrote:I don't see why inside air can't be recirculated without drawing outside air in.  A simple air return from the upper lever to the basement would achieve that.


That's true, although the warm upstairs air will typically have more entrained moisture than the air in the basement. How much depends on many factors (humans, showers, cooking, plants, opening doors and windows, etc.).

But I think it's more an issue of volume. Usually a basement has much less air volume than the upstairs areas of a home. So, I think the cooling effectiveness would be greatly diminished.

I can give a hands-on example. For years, in our relatively dry climate, I mounted an old furnace fan in a basement window (exhaust mode), opened cool-side upstairs windows, and sucked all the air out of the house for a few hours. This would not only remove the warm upstair air but would also cool the upstairs surfaces and wall/ceiling materials. Very effective. Until our summers started to shift to a higher humidity. One day I went downstairs to check on the fan, which had been running for hours, and found puddles of water on the concrete floor. I was actually hunting around for a leaking water pipe when I realized my ventilation system had created an water distillery in the basement. After that I created a cross-draft system using the main floor and upstairs only.  
 
John F Dean
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To be sure, I am not a believer that this will work enough to make a real difference, but some flexible duct work,  say from an upper window to a basement window with a box fan at least blowing up from the basement (and maybe at both ends) would  provide for an interesting experiment at little cost.  Where I become a skeptic is while I am sure the initial air flow will be quite cool, i am less confident  as to how long it will take the basement too cool the air from the upper level once the initial volume of air from the basement is exchanged.  My guess is that there will be minimal gain in the long term.
 
Douglas Alpenstock
pollinator
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I agree, it's definitely worth experimenting with. That's how you figure out what actually works.

And it's worth the effort, because you can create cooling solutions that use 80-90% less electricity than AC.

So, apologies if I come across as negative. I'm just pointing out a few potential pitfalls.
 
John F Dean
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I didn't see you as negative at all.  In the end, we end up,in the same place.
 
pollinator
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To do it right you'll have to look for a place you can make a large duct from basement to top floor. Perhaps through a closet or sacrifice the corner of a room. Bigger the better.
Close to the center of the house if you can.  Just guessing 12 x 24 minimum. Mount the fan in the basement pushing cold air up.
 
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I like John's idea of trialing a temporary duct from a basement window to an upstairs window.  I'd put it on the East or North side so the duct doesn't get heated by sunlight.  Blow air to the upstairs and see how much of a difference it makes.  I'm guessing it will feel colder where the basement air blows in but I'm not sure how much colder it will make the room over the course of 4 hours.  

If you have a shady north window in the basement, you could also try just opening that window to let cooler air in and open an upstairs window to let hot air out.  The whole house would act like a chimney to exhaust the warm air in the house.  In that case you're replacing it with shaded outside air which may not be much better.

Regarding the upstairs air having more moisture in it, I'm not sure about that.  I've always been led to believe that the dewpoint stays relatively similar in the whole house (excepting bathrooms and other moisture point sources).  Temps may change and relative humidity may vary accordingly but that the basic dew point would be the same.  So the hot upstairs air, when cooled down, would become colder and wetter but match the damper colder basement air.  Maybe I'm all wrong on that concept though...

They have made attic fans that blow massive amounts of house air up into the attic.  These, I think, are intended to work in conjunction with opening windows on the north side (in the northern hemisphere).  The goal is to quickly remove hot air in the afternoon/evening and replace it with nicer outside air.  I'm not sure if they're still sold.  And they probably only work well in some climates.
 
pollinator
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The full basements of both old houses I take care of warm up relatively quickly w/out using any fans if I leave the outside basement door open.  This happens when we leave the door open by mistake or when there is a lot of traffic in/out during the day. By relatively quickly I  mean at 95F. outside, the basement will go from 65F to 80+F in two days, three at the most. This leads me to believe there is not enough temperature drop in the basement to help cooling the upper floors much.

Whole-house fans which were sold for a few years to install into the attic stair hatch in an upstairs hallway work. At least they move air in through the living area, blowing it into the attic and out, when there is sufficient openings for intake and outlet. They were removable for winter. You can certainly cobble together something to move a lot of air if you want. Cut a hole or three in the walls of the upper living area that let into attic "crawl spaces" and install some big fans. Do think through how much air you're going to move and how big the exterior openings need to be. I don't remember the specs - it was 30+ years ago when those big fans were in vogue - but since big bathroom fans are over 500CFM and stove exhausts easily top 1000CFM, you may be looking at 1500+ CFM. I would advise some actual in depth research of that type of installation.

Large stove fans _require_, by code, makeup air inlets from the outside into the kitchen in order to not cause problems elsewhere in the house, especially with other combustion appliances like water heaters but also with any other HVAC in the house. Radon specs for your area should also be checked because that big a "suck" will go looking for air to draw and it will find places you may not want it to.

It's not hard to move air. The question is whether it will do what you want. For a whole-house fan(s) to work right you must always open the "intakes" whenever you power on the fan. That means a large window in all ground rooms you want to condition and quite possibly the front and back doors. Smaller fans avoid some of the more thought provoking problems (like violently slamming doors), but you must still think out carefully what you expect it to do and size it properly. This stuff can be found on the net fairly easily.

I like erector set tinker toy lego stuff as much as the next guy, but I would not go to fans first. For that, start by keeping the heat out. Not so many Rambo points, but way more reliable and cheap to run and maintain.

Somebody mentioned awnings. Yeah! Any sunbeams that get into your living area carry  HUGE amount of heat energy. Blinds and curtains are better than nothing, but they just collect the heat in that little space adjacent their exterior facing surface - but still inside your living area.  

Second, passive ventilation. That means _easy to use_ openings, windows and doors, in every room. Windows and doors that function like new _and_ that are designed well enough to be easily usable by the residents and with the opening large enough to be useful _and_ that furniture is not arranged to block convenient access to the window.

Third, insulation. This is where it gets really sweaty, dirty and as you search for the next 5% you start to pay money. Do spend 10-20 hours reading up on modern building science roof designs. It's not _exactly_ rocket science, but there are a lot of options and details. You need the overview and concepts in order to make informed choices for _your_ situation. Probably the first one is vented attic or sealed attic. There are arguments both ways.

One almost free option (but lots of crud and sweat) for "unused" areas of an attic is tin foil. Radiant barriers depend on having at least 3/4" clear space on each side and you can provide that relatively easily in the attic. Tin foil the whole underside of any exposed interior roof structure that gets sun. Spray adhesive can work or staples, but with staples you need some kind of "washer" to staple through - staples will just blow right through tin foil. "Shirt" cardboard in 1-1/2" squares or circles works; or larger  if you're using a hammer stapler and have shaky aim.  If the space is really and truly unused, you can tin foil it's floor as well. I did this 12 years ago and it made an unbearable attic cool enough to work in. As I recall, using the cheaper thin foil works fine once you learn how not to tear it all the time. If you're ham handed, get the thick industrial strenght stuff.

Whether you insulate the rafters or the ceiling or both depends on stuff. That why you need the in depth overview. As always with insulation of any kind, seal the holes first. ALL OF THEM. Dirt and sweat aplenty. Pipes, wires, poor joints. Those holes will just blow "enemy air" around your pricey insulation. The have to be eliminated.

This doesn't need to happen all at once. Shade first. Ventilation. Tin foil if you go into the attic and pass out. Then think about design and material options for insulation. One thing that all insulation has in common is that it does not require power or maintenance. Just repair when somebody opens a wall and messes it up. Your house may have some insulation - gotta get behind the walls to find out. You could try poking up from the basement or poking down from the attic (around the outer walls, that is). You may be able to see whats in the attic floor (ceiling when looking up from below; but it may not be the same in all areas.

Are you starting to wonder about shade trees? <GGG> Tall bushes or vines along the sun walls of the house can make a big difference, also.


Cheers,
Rufus

 
Joshua Frank
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Just wanted to thank you all for this excellent advice. I am digesting all the suggestions and thinking about which ones I can implement, and in what order.
 
John F Dean
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Hi Mike,

Those attic fans are still sold.  I have one in my house.  Here is the southern tip of Illinois it gets hot and humid pretty fast.  The fan delays the need for air conditioning.    I have the circulation arranged where it can vent the whole house or just the attic.  I also have the benefit of three huge Oak trees to the south of the house.
 
Rufus Laggren
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> existing insulation...

Another way to try to see what you have in your walls is with a good small flashlight, a kitchen knife or some such "poke tool". Take the trim covers off electrical outlets, switchs, etc in exterior walls and gently poke around the edges of the box and see what you can see.


Rufus
 
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