Cooling the house with the basement.
 

My house that was built in 1906 doesn't have A/C, last summer we put 16" of insulation in the attic and that helped both with keeping the house cool in the summer and warm in the winter.
We are pretty good about keeping the heat out in the summer, closing windows up at 6am and pulling shades to keep the sun out, but there was a week or so were it was 95F or more in the day time and never got cooler then 80F at night with high humidity, last summer at some point we brought the dehumidifier up from the basement to dry the air in the living space, this worked well but made the living space warmer, so this hot humid weather made me tempted to get a window A/C unit, then my room mates brother, who is a HVAC installer suggested last week that we use the furnace to cool the house with basement air, I've always snubbed my noise at this idea but thought that I would give it a try, so we taped over the safety switch that keeps the fan from coming on if the furnace is open to the basement then installed a twist timer across the two contacts that turn just the fan on (our thermostat doesn't have a "fan" setting) I also installed another air filter to keep dust from the basement out of the duct work so with the dehumidifier running in the basement we are now pulling cool dry air from the basement in to the rest of the house, running the blower for 10-15 minutes is about right, the humidity readout in the basement starts out reading 50% and jumps up to 70% as the air is moved around and takes about an hour or so to get the humidity back down to 50% in the basement, at that point I repeat the cycle.
The theory is that even tho the dehumidifier is warming the air, the basement walls are sucking up that heat, cooling that dry air, it takes time but it has kept our house very comfortable, right now the indoor readings are 77F with 54% and the out door readings are 79F with 84% humidity, the over all feel inside is very comfortable, outside it feels hot and muggy.

Another way to do this is to have a fan (or fans) exhausting air out of the attic, and close all the windows in the house except one in the basement; and this will slowly pull cool air up through the house during the day.

Close the shades and/or curtains especially on the south and west side of the house (or north and west if you live down under!) to limit the heat build up from the sun.

And yes attic and wall insulation help a great deal, too.

Great idea Ryland. Is there any chance we could get pictures and a bit of a write up on how we could do this ourselves? I'm definitely interested. My basement is a nice cool ~50F, and my upstairs is around 80F lately this week!

And it's working for an extended period of time? This is fantastic! It's about a million degrees in my house and 99% humidity. Unfortunately the temperature in my basement increased by about 20 degrees the moment I put the insulation up so it won't work for me.

We've had temps in the mid to upper 90's all week and out door temps are only dropping down to the mid 80's, last night it got down to 83F and this idea is starting to fail, up stairs temp is up to 88F at 47% humidity and basement temp is up to about 70F, it is working really well to keep the house dry, even in the mornings when the temp is about the same inside and outside the humidity outside makes the air feel thick and gross, I'll keep doing this but due to the ever rising temps my fridge is no longer keeping it's cool, so I borrowed a window A/C unit to cool the kitchen... trouble is this window unit will cost $4 per day to run so I'm only going to use it as needed.

I don't have a full basement (about 400sf of basement for a 2,200sf house) so I think that a full basement would help a great deal, but keeping the living space at 45% to 50% humidity while it's 70-100% outside has been very nice, but we just don't have the surface area in the basement to cool the air fast enough to combat a week of hot humid days.

I'll do a better write up later, but what questions did folks have, or points that they wanted clarified?

What if you ran a fan downstairs just to circulate the air within the basement? I would think that that would improve the heat transfer and cool the air down faster.

I'm most interested in how you seperated the closed loop from itself to make it exhaust into the basement and also suck from the basement.

Path of least resistance! I left the filter in the furnace but took the side off the furnace and duck taped a new filter to the side of the furnace to filter the incoming air, so it doesn't pull 100% of the air from the basement, but it's less work for it to pull basement air then it is to pull air from the cold air duct work, I then just left the basement door open and you can feel the draft if you stand in that door way!
I thought about doing something to move more air around the basement, but the dehumidifier is already blowing air around and it takes a while for that to catch up so I figured that it was doing a enough to keep air moving.
The window A/C unit that we ended up borrowing is working really well, it dehumidifies more then it cools and it only takes a few hours to dry out the air in the upper part of the house to 35% to 40% so I'm wondering if it is even worth moving the air from the basement up in to the rest of the house.
A/C unit draws 1,200 watts and dumps all the heat outside while cooling and drying the air inside, seems to drop the humidity by about 20% per hour (not documented, just a guess).
Basement Dehumidifier draws 600 watts while running with the compressor on and drys the air by 15-20% per hour when brought to the main floor of the house.
Furnace fan has a 1/4 or 1/3hp motor and also draws alot of power, not sure how much but I will find out next time I have a clamp on amp meter handy.

So what we are thinking is, this fall when window A/C units go on sale we will look for something like the Haier model that has an EER (energy efficiency rating) of 12 EER while energy star is anything over 9.4 EER, I would then be tempted to install it on either a timer or a humidistat so that it turns off once the humidity is down to a set level in the house, goal being to dry the house out when it's hot and humid, not to get it to feel like a walk in cooler, of course it also seems best to run any sort of A/C at night, when it's cooler and the humidity is at it's all time highest, as the heat is transfers in to air is improved with humidity.

I just checked the amp draw of the furnace fan, 5.8 amps! so it's drawing around 650 watts while it is running! combined with the dehumidifier that draws around 600 watts while running the window A/C is looking like a better and better way to dry our house out.
Of course the dehumidifier keeps the basement dry year round, we have it painted with dry lock paint on the walls and epoxy paint on the floor with plastic in the crawl spaces that is sealed in with spray foam and calk, even with that the dehumidifier runs a few hours per day where before the dry lock paint and crawl space plastic it used to run nearly non stop.

So my conclusion is, if you just want to dry your house out and cool it a tiny bit, an energy star rated window A/C unit really is a good way to go, but if you want to do it on the short term cheap and already have a dehumidifier then using your furnace to cool and dry the rest of your house does work up until that point that your basement warms up, this is of course dependent on the side of basement you have, the size of house and how well everything is insulated.

I'll chime in on this. I've seen others do this and so tried it earlier this summer. I didn't use the furnace because at the time it used a motor that sucked about 800 watts or so, I just ran a fan from the basement up to the next level and another from there to the top floor. The basement was about 60 degrees, upstairs about 80, after about 6 hours the house was a uniform temperature, the next morning the basement was 65 and upstairs was high 70's, ran it again and then soon enough the basement was 70 and the upstairs was still hot. The cycle continued until I realized that it wasn't going to work out too well. I usually spend time in the lower level and decided that it was better just to be in the lower level of the house(not the basement) for using the computer, reading the paper, etc. So I let the upstairs be 82 degrees while downstairs was 75 or so and comfortable enough and didn't bother firing up the A/C. I have a guest room downstairs with a bed and ended up sleeping down there and it cut the A/C usage down to days where it was 85 degrees or higher. I also only ran the A/C when the house was going to get above 40% humidity and on the cooler days I'd let it get to close to 50% and allow it to run constantly until humidity was in check again.

I later did a radon test and learned you really shouldn't be sucking basement air into your living areas, especially if you are using a furnace blower to do it, by putting the basement under negative pressure you are sucking air through the small cracks in your basement, the drain tiling, and pulling in air through the soil which is a great way to not only introduce radon into your basement, since you are sucking that basement air throughout the house you are putting that radon everywhere. Western Wisconsin is in an area where if you are doing what you are doing, you really should check your radon levels. My living area including lower level doesn't have much radon but I wouldn't sleep in my basement and I won't be running any fans to push that air upstairs either.

Since hot air rises, I've also been thinking of going the window A/C or mini-split inverter heat pump route too as my A/C is from 1986 and probably in the 10-12 SEER range. I swapped out my shaded pole blower motor for one that is a split-capacitor design and went from 6.6 amps or so to 3.3 amps at air conditioning speed(800 CFM blower at 1/5 HP). More savings at the slower furnace speed when comparing both motors. Either way a window A/C uses so much less power and only cools the area we want it to cool so I think you are going the right route.

Problem is that I don't have the up/down sliding windows, mine are tall side-to-side sliders and I can't find a window A/C to fit them so I'd have to go for a wall A/C which takes me out of the $200-400 or so 10.8 or better EER A/C unit market.

They do make window AC units for horizontal sliders, but for whatever reason they are 2-3 times the money. I have seen them here in Canada at Sears, and this time of year you may find clearance prices!

Yeah, I'd rather install a mini-split heat pump for that reason, not much more than a tall window A/C and much more efficient, plus the horizontal slider is too tall for all of the casement style A/C units I've seen and anything this tall would be a serious eyesore anyway. I wouldn't mind installing a window A/C in a wall but many can't accommodate that and I'd rather not need to replace a big hole in the wall(high cost) when it comes time to eventually move.

I tried using fans at night to cool our house but last summer it was still warmer outside at night then it was inside the house, or if it was close to the same temp it was much more humid so it felt damp and hot, that is why using the window air conditioner to dehumidify the inside of the house seemed to work so well.
I've been thinking about making a dedicated hole in the wall for a window A/C unit but is that the best route? would a mini split be better? it would be on a north wall of the 2nd floor.

There's a lot of difference in specs of mini-splits from one model to the next if you compared across the same cooling capacity.

If cooling is your main concern look for the best SEER rating.

If heating is your main concern look for the best HSPF rating.

Mini-splits will cost more than a window or thru-the-wall unit, but they will be more efficient.

For me, at this point, the only reason I would get a window air conditioner would be to make something else out of it.

-AC_Hacker

Ryland,

Any updates on your window a/c in the basement system?

Are you still using it?

What I ended up doing was getting a window A/C unit and putting it upstairs in a window and it works really well to cool the whole house, the main thing is keeping the house dry, It's at the top of the stairs so because cold air sinks it also cools the downstairs and drys the air out down there.
I ended up going with a new air conditioner that has a remote, at first it seemed kind of hokey but the remote has a temp sensor in it and as long as it can "see" the air conditioner it can control it, so I set the remote's temp and it clicks on as needed, it also had some programming options, like run for an hour or two then turn off or wait a few hours then turn on.

The window A/C also drys out the house really quickly, I have a in door out door thermometer that reads humidity as well and it does a much better job of keeping the house dry and comfertable then the basement dehumidifier does.
Having that info of temp and humidity both in doors and out doors is priceless! sure it might feel cool because of the breeze but opening that window might just make the house hot and muggy.

I also took my infrared thermometer and checked the surface temp of my basement walls and they are around 60F in the winter and 70F in the peek heat of the summer, so pretty good for a 107 year old house with sand stone foundation.

Thanks for the update.

I liked the idea of cooling the basement further with the window unit, and then circulating that through the house with the hvac fan. As I would think it would use less energy then operating the big a/c unit.

But maybe it's not worth the effort.

If you need to cool your basement then cool your basement and if it's hot out and your basement is damp then dry it out with an air conditioner dumping that heat outside.
Having the A/C up stairs then non of that cooled air is making it's way to the basement unless I open the basement door way and at that point I might still have to put a fan at the top of the stairs.

What I learned tho is that the energy that it takes to move air from the basement up in to the rest of the house is not worth it and that it takes the least amount of energy of course to cool the part of the house that you want cool or in my case to make it dryer/less muggy.

I keep a single 40 watt box fan handy in the summer to move the air conditioned air around the house, I suppose I could switch on the furnace fan for a few minutes but at 600 watts for the furnace fan I'm not sure it's worth even running it for 5 minutes, but I might try it, I think it would take about 15-20 minutes do to a full air exchange and even out the air temp in the whole house, but also having the Air Conditioner up stairs at the top of the stairs lets the natural convection move the air for me.

Ryland,

The approach you have settled on is very close to what I do in my home. I have a 12000 btu window a/c in the second story that I set to run at about 5 degF above the central air thermostat on the ground level of my home. When it's hot outside, the small unit runs much longer than the central unit, but every once in a while the central 3 ton unit unit kicks on for a short time.

From first glance, this approach seems like it is ineffective, since the larger unit is certainly more energy efficient than the smaller one. In practice, it works very well and saves me energy and money. The window unit does an excellent job of dehumidifying the air, and the central unit basically just mixes and cools the already dried air quickly when it runs.

As they say, it's not the heat, it's the humidity, get that humidity down and your house feels cooler and that is really where a small window a/c unit that cycles on and off helps a great deal by drying the air and dumping the heat outside.

Where would you put that AC unit on the second floor? I wouldn't want to put it in a bedroom just because I'm not a fan of freezing my rooms. Could I stick that in the main bathroom upstairs? I guess it wouldn't matter where you placed it?

Higgy,

It all depends on your floor plan and where the small unit would do the most good. In my place, the top floor is just one long room. It has windows at each end wall of the house. I put my unit in the end where the stairwell comes out. When it runs, the cooler air fills up the stairwell first, then fills up the whole story with cooled air. It is set warmer than the central unit below, so it won't try to cool the whole house. It functions as a dehumidifier more than anything.

When the central unit downstairs kicks on, the dried return air from upstairs takes much less capacity to cool because the central unit doesn't have to condense liters of humidity. The central unit runs for less time each cycle and cycles less often. It saves energy because even though the upstairs window unit isn't as efficient, it's not cooling the air upstairs to the same lower temperature as the larger unit downstairs. I'm not trying to "freeze" the air upstairs.

This is kind of the opposite of the original idea of moving cool basement air to a higher level of the house. If you have a basement which occupies a large portion of the footprint of your house and can circulate this cooler air to the top story of your house efficiently, you would achieve a similar result for much less energy. However, Ryland found that his circulator fan consumed as much energy to run as a small window ac unit and did not dehumidify as well as he wished. As for me, I don't even have a basement...

I have a 2nd living room upstairs, so I have the window Air conditioner in that room, my brother puts his in the window in the upper hallway at the top of the stairs.
You release a lot of water while sleeping and bedding holds a lot of water making it uncomfortable so drying out your bed room makes sense to me, the idea is not to chill the house but instead to dry it out and dump the heat outside, I have to have the air conditioner run a lot longer if I want to chill the house, but if I set it to dehumidify then it drys the air pretty quick, making it feel cooler without being cold and without using a lot of energy because the greater the heat difference is between two areas the greater the losses.

Natures Airconditioner
 

I live in Upstate New York. Very hot and humid summers. I have a full renovated basement that stays a constant 54 degrees all year long. I have tried to fan the cool air upstairs (Ranch style Home). This works well on 80 degree days but on the hotter July and August humid days (90+) the upstairs temp climbs to 85+.

I have a forced hot air gas furnace with metal duct work and vents in each room on the main floor of my home with no fan only mode on the thermostadt.

So, I went to Home Depot, purchased a cheap energy star rated radon pump and 4" plastic pipe. Mounted the pump on my basement floor, in the bathroom near the incoming main house water supply line. (The coolest part of my basement)
I cut a hole in the ceiling and metal duct work, I installed a 4" vent ring used to mount on the roof for exhausting the radon out, and pumped that cool air in my duct work. Works like a constant A/C is on, cool air all the time, basement is less humid and all is good... P.S. Used a radon test kit first and have radon dector in place.

Terralore,

That's what I'm talking about! Can you elaborate on the strategy you use to operate the rig as well as your overall impression of comfort and bang for the buck the rig provides? There are many members that could benefit from such an upgrade, but many are pessimistic as to whether it's worth the effort and expense.

Great to hear its working out for someone. I must say I'm surprised to hear that your basement humidity hasn't increased though.

I used to think the same thing about my basement until I started to actually measure and record temperatures in the basement on a regular, periodic basis. That's when I came to realize that the basement temp actually did change. However, it was always a comfortable margin cooler than the rest of the house.

This is really a cheap straightforward hack. Way to go!

It would be useful for us all, if you kept a log of the upstairs temps and also the basement temps. A data logger would be nice, but a notebook with date & time & temps can go a long way.

Best,

-AC

Any updates on your setup Terralore?

It's been so hot, my basement temp is about 72 degrees. So not much help to be had from there.

My basement stays pretty cool all summer long. I don't think it ever gets above mid 50s... I'd like to try something like this.

New furnace!
Instead of the fan drawing 650 watts like the old one did, the new one has a low speed option that draws 70 watts, combine this with a single window AC unit at the top of the stairs in the 2nd floor of my house and the house is staying very comfortable!

The key here is drying the air first before you send it to the living space. One year I had the bright idea to 'suck the nice cool air from the basement' to the rest of the house and about killed us all the temperature rose about 20 degrees in 20 mins. due to the humidity / enthalpy - I turned that off real quick ;) lol

The temperature shouldn't rise. The moisture content(as measured by the dew point) in a house with all open doors should be nearly the same. If you were somehow causing a negative pressure pulling outdoor air inside I could see this happening but other than that I can't make sense of this.

I tried this once but once the cooler downstairs air mixed with the warmer air upstairs, eventually the heat upstairs overwhelmed the downstairs temperature after a few days and the basement wasn't cool anymore and there was little cool air left to lose downstairs to cool the upstairs and the air conditioner was powered back on. ..put that together with dew points in the 70s outdoors and I needed to run the AC to bring the dew point down to a safe level in the basement to prevent mold. So for me, it worked for awhile and is plenty good when it isn't in the 80's outside and there is a good cold thermal mass in the basement. It gets exhausted quickly with solar exposure in my case.

I'm referring to the fact that without drying the air in the basement first, I raised the relative humidity in the living space most likely close to 100% which made it nearly impossible to sweat. So I was exaggerating about the temperature rise as it is really just a 'conceived' rise in temperature. 75 degrees in 0% humidity feels like 69 degrees and 75 degrees at 100% humidity feels like 80 degrees. I'm thinking it was 85 degrees at 30% or 40% humidity that day so you can imagine how we felt when the humidity shot up quickly to 90% to 100 %