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Would You Heat a Room With a Heat Grabber?

10/2/2009 1:54:57 PM

Tags: question to readers, heat grabber

Heat GrabberMost of us prefer to heat and cool our houses or apartments with simple-to-use machinery such as furnaces and air conditioners. The next level of difficulty in heating might be the use of a woodstove for heat, or opening and closing windows for cooling. But you can go one step further and build a heat grabber.

A heat grabber is a simple box, painted black, that hangs outside of a south-facing window. The box is hollow and insulated. The sun strikes the black flat face, heats the air inside the box and the hot air flows naturally up and into the room. Some folks add a small fan to the unit to move the air further into the room, but it can be used effectively in a small room even if you don’t use a fan.

So, would you be willing to build and use a heat-grabber box to heat a cold room in your house? If so (or not), tell us about it in the comments section below.

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3/25/2010 11:49:28 PM
I built a similar design last fall. I ligned the inside of the box with soda and beer cans painted with flat black bbq paint. The whole box is approx 3ft wide by 5ft high. I used insolated 4 in dryer duct to vent it into the house. On sunny days when the temps are above 20 which is most winter days I can top out at 110deg. If its over 30 out i can get 120+deg air. The front is plexi with a slight bow design. The cans give the heater a larger serface area whiches increases heat out put. I plan on making a few more as this 1 heater saved 100 gal of oil this year compared to last. E mail me for pict and more info.

3/15/2010 4:02:37 PM
Absolutely! We live in Maine, and unfortunately our old house only has two small windows on our south facing wall. I've been thinking about this project over for about three years. I'm hesitant about cutting holes in the house for a wall mounted unit, so I'm going to make a window heat grabber first.

1/8/2010 10:02:05 PM
I built this heat collector in Sept. 09, installed it Oct 1st,then enjoyed only 6 days of sun in Oct. (Chicago area) Those 6 days produced great heat. Days of sunlight are less than I expected. It is now Jan 8th, 2010 and since Dec 20 or so we've had 4 good days of sun. I sure hope this year is unusual. Last week I measured 94 degrees input air, while outside temp was 20 or so. I have the duct work stopping at our inside double hung window so we can close the window when it is not producing - a must - it is cool when not sunny and at night. I want to build two more for south facing windows, one more this winter still. Thanks MEN, keep up the good work.

1/8/2010 4:36:21 PM
I'm thinking of something like the solar grabber that fits through the wall and hangs on the side of the house but I think this is a great idea .Probably the more surface used the more heat you get . When money is so tight the looks of the grabber and other energy saving devices aren't as important as the looks of an empty bank account and wallet. Keep up the good work and let us know more. I've installed the solar shed lights inside the house as a start to reduce my electric consumtion . They're inexpensive , easy to install and since lighting uses a lot of energy it helps us reduce that bill. They can be left as is or dressed up . I used an "easy wireless switch" from tv ad to operate them .These lights works great for power failures too . I'd love to go total wind and solar, but can't afford it all at once so I'm taking tiny steps .

1/8/2010 11:45:13 AM
I've ofter thought this was a great idea, until I realized my house has large south-facing windows. So on sunny days (the only time a solar hot air system would be running), my southern rooms are already warm, and my northern rooms are bedrooms where hoone spends time during the day, so who cares if they're cold? Now, my last house was a different story, since it had only one south-facing window, with a lot of morning shade. If you have a home that is poorly designed/oriented for passive solar, this could be very useful. But I'll have to save my pennies for a system that stores the sun's daytime heat into the night, and summer heat into winter.

Russell Meyers
1/8/2010 11:18:44 AM
My steel casement windows won't allow for this design. However, I built a large solar collector on the back of the house over the last couple of weeks. It works great! In the afternoon, I've measured temps in the collector up to 96 degrees F! Besides, it blocks wind from an uninsulated wall and the crawlspace opening. (Structure is 8ftx8ftx15ft, all wood and plastic sheeting.) This one is temporary and experimental. Precursor to a large solarium, combination covered patio and greenhouse attached to the house. I'll be building that over the summer. Going to include upper vents and solar chimney for summer cooling.

1/8/2010 11:15:55 AM
I am building one of these to collect morning sun. My house is shaded from afternoon sun where I have windows. I also am building a green house on the south right up against my house. It will be a huge solar collector to help heat my house.

1/8/2010 9:32:39 AM
For those serious about solar heating should join the following Yahoo! groups: Also visit: I have one small solar air heater in operation and now building a larger one (8' x 12'). I live in cold MN. Chad Urvig

1/8/2010 9:22:08 AM
This sounds fantastic: I heat my hole house with a ventless gas fireplace and it is toasty for very little money. I keep the heater in the living room and it heats all the way to the bedroom about 50 feet away. The bedroom is a bit cool, by choice. Sometimes I do wish I had more heat on the realy bitter days. If I pump up the living room it will be too hot in there. As luck would have it one window is south. I am going to try this if it is not too entalied. But if I can build a large chicken coop alone I think I can handle this. So now I have no phone bill no cel phone bill and 1/4 the heat cost, can I go any lower?

11/16/2009 8:31:13 PM
Back in the 80s I bought the plans for this from MEN and built one. It worked pretty well pumping heat into my dining room window. Unfortunately for me I did not have a good south facing window, the dining room was more west-south west. Still, it pumped hot air into the room on sunny but bitter cold days in the winter! I recommend it. Jim

10/8/2009 4:01:30 AM
Sorry I forgot to add -we live in maine.still have to add the dust protectors,and outside dump vents.I just covered the holes this summer inside with radiant barrier pieces for the time being.we used aluminum flashing.

10/8/2009 3:57:28 AM
We built one also last feb 08'. The heat temp coming into the room was 117*. We built it from safety door glass,painted inside black-insulated,metal strips covering all the wood strips & baffles.We hung ours on the wall in the dining room- cut the wall holes.We plan to build one even bigger on the living room wall.

10/7/2009 3:13:16 PM
Built a similar one last February. On the 1st day air entered unit @ 69 degrees and exited at 153 degrees (Outside temp was 43 degrees). After that, we turned off our traditional heat when we left for work each day and turned it back later that evening. At most, our interior temp declined 4-5 degrees during the day. Substantial power savings.

Gordon Henry
10/7/2009 1:29:46 PM
Joan, If not built correctly it will lose heat at night. But it's an easy fix. Install 1/4 or 1/2" hardware cloth (screen) on the intake and outlet ducts. Then mount some 6 or 8 mil plastic (top edge ONLY) to the ducts. Outlet (hot) on the house side, inlet (cold) on the collector side These will act as check valves for the reverse air flow at night. The statement about the fan was partly right, the air out will seem cooler. But the reality is that you will get more heat out with the fan. I proved it to my self with a non-contact thermometer testing the box and glazing with the fan on then off. The law of thermodynamics (or what ever) says that the higher the temperature in a container the more heat will be lost through the walls and glazing. The simplest way to hook up a fan is a small 12volt solar panel and a 12 volt fan. When the sun shines the fan does to and visa versa. Gordy

10/7/2009 12:54:17 PM
We just bought property on a lake in central British Columbia and are hoping to fix up the old house for year round use. We have good southern exposure and although winter days are short, they are usually sunny. The zone is USDA 2 which means - 40 F to 50 F for, possibly, weeks. Very little wind, though. Like Joan from Saskatchewan (I grew up there, love it, but the wind is too much for this old hippie) I want to keep horses, goats, chickens, and I already know that horses do okay outside at these temperatures (they grow a thick coat) so a bit of solar warmth in their shelter will feel cozy, I think. So, yes, bring on the plans.

MA Doc
10/7/2009 12:03:00 PM
I saved plans for a very similar unit from MEN in the early 80s. Haven't built it yet, but keep thinking of it. And with the demise of my heating system last week, as well as having already spent $20K on replacement windows this year, I think now may be the time to reduce expenses wherever possible. Tas (northern MA)

10/7/2009 10:13:54 AM
I built a window solar collector years ago when I lived in the Santa Cruz mountains of California. Mine was a basic modified design I got from the 60's Whole Earth Catalog (hippies needed heat too). I used a very old 4'x8' CDX (exterior grade) plywood sheet and built a 2"x2" picture frame around the edge. I cut out 4" holes at top and bottom. I then used black mastic to attach cat food cans for heat grabbers to the face. I painting the cans flat black as well. I capped it all with old window I had laying around and caulked it tight. I was lucky(???) enough to live in an old cabin with a crawl space underneath (brrr). I attached flexible dryer vent to both of the 4" holes I'd cut in my plywood base and ran one through a window using a piece of 1"x6" to hold the vent and block the rest of the window opening. The other I routed under the cabin and through the floor on the other side of the room for my cold air return. A little insulation wrap on the ducting and the southern sky gave me all the heat I needed. Maybe a little crude, but that little solar collector worked extremely well. Natural convection is all you need. I don't recommend a fan as accelerated air is cooled air. It worked well for me and I think it's still there.

Bill Ross_2
10/7/2009 8:04:53 AM
Obviously, this is only effective during the day, no matter where you live! But at night, we should all be sleeping in flannel sheets and down blankets with the heat off anyway! I'm going to try it. I've struck out, so far, finding a welder to follow the MEN plans for a wood stove. :(

10/5/2009 8:22:33 AM
I have to agree with Joan on this one. Steve I would suggest that aluminum would be a better choice than using steel. I lived in Fredonia New York back in the early 70's and made a very effective solar hot water heater that reduced my gas bill noticeably even in the winter. I suppose that some areas of western New York have serious cloud cover during portions of the winter but I believe that the heat grabber would see enough sunshine to make it an effective boost to your heating which would reduce your heating costs. Try it out and see, what have you got to lose? If it works you ahead of the game and will certainly reduce your use of finite resources.

10/4/2009 12:13:34 PM
As long as your not in a climate like mine in WNY. We get way too much cloud cover during the winter months, for any solar applications to be viable alternatives but we too make up for it with wind. If I were in say Saskatoon like Joan I would want to amp the grabber up a notch with some simple additions. Like adding some 1/4 inch plate steel to the inside back, painted black to really get the BTU's super charged. I might even add that steel in an according fashion to increase surface area. Then that baby would probably serve the dual purpose of being able to cook the chickens as well as heat them. LOL

Joan from Saskatchewan
10/3/2009 11:59:49 PM
Absolutely! It is on the list of "projects to investigate and perhaps try" that I have gleaned from Mother. Trying it on our Homestead would be a real test: we are a three-generation family unit of newbie Homesteaders living in East Central Saskatchewan, Canada. We fled the city life last year to learn how to Homestead. So much to learn! Mother Earth News really helps with the learning curve. We have a small herd of Dexter and Dexter cross cattle and Chantecler Chickens to practice on. Lucky them! They all need proper housing and we are looking for cost-effective and affordable ways to house them and protect them in winter. Alternative methods appeal to my adventurous nature! Especially wind and solar – we have so much of both! Next year we are planning to build a proper chicken house for our Heritage Breed Chantecler Chickens (my vote is for cordwood). Meanwhile, I am already thinking of ways to help keep their current house (a grand overstatement, I assure you!) warm during our extreme winters. A heat grabber sounds like a great idea if it works in our harsh winter climate. Last winter, we spent a lot of time at minus forty Celsius (same temp as minus 40 Fahrenheit!!). This number is not counting wind-chill, which was often in the extreme ranges as we get a great deal of very strong winds roaring (and I do mean audibly ROARING)down from Northern Canada and the Arctic. Imagine minus 40 with 50 kilometer winds.... windchill, indeed! This winter is supposed to be much like last year. My one concern is will the heat grabber actually work during the winter in our extreme climate conditions or worse, function in reverse at night due to wind or thermal dynamics, or some other factor we aren’t aware of? We don’t want to open the coop one morning to find "chick-sicles"! Has anybody used one of these things in Northern climates (slightly south and east of Saskatoon SK) before? I am still researching...thinking….but the idea really appeals!

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