Passive Solar Heated Home Design


pdf of Mears "Solar Heated Home Using an Attached Greenhouse & Woodburning Stove"

This is an 11 page paper of an actual system designed and implemented by Prof. David Mears, Agricultural Engineer, Rutgers University. It was retrofit to a Civil War era house in New Jersey at minimal cost in 1980 and, per Mears, has kept the residence at or above 68 degrees F for 25 years without once requiring resort to the backup oil heating system.

I'm intererested in the topic of energy efficient homes and sustainable agriculture, in general, in addition to, and in complement to, the idea of home automation.
Here's a background story:

Yahoo story on Mears House

LiveScience Story on Mears Greenhouse/heatsink house

Real 'Green' House: No Heating Bill for 25 Years Sara Goudarzi
LiveScience Staff Writer
Sat Apr 22, 9:00 AM ET

When David Mears and his wife Dorothy put their house up for sale at the end of last year...The main attraction was the fact that the couple hadn't paid their heating bill for more than 25 years.

That's because they hadn't received one since 1980.

Using his knowledge of alternative energy sources for commercial greenhouses in response to the energy crisis of the 1970's, David Mears, a professor of Bioresource Engineering at Rutgers University, virtually eliminated the use of fuel oil for heating his home.

Multiply that ...

According to the Department of Energy, more than 85 percent of all the energy consumed in the United States comes from fossil fuels, including coal, oil, and natural gas.

Some 2,700 pounds of carbon per person each year, or 18 percent of greenhouse gas emissions, come from operating individual homes, the U.S. Environmental Protection Agency estimates. Most of emissions from a residential home come from operating a typical heating, ventilation and air conditioning system.....
I find it interesting that many people look at the cost of fossil fules as the only costs for heating systems in many areas. Having grown up in a home where we used a central wood furnace with hot air, I know a bit about wood heating. The article does describe that they used 3-4 cords of wood per year, in addition to the solar gain, which in the winter primarily took care of the greenhouse, and having to use oil when they were away and could not run the woodstove every day. So, the title of the paper is a bit misleading.

They further stated that the wood came from deadwood on the property. There is time and energy involved in getting that wood in and cutting and splitting it. I don't know of many homeowners in non-rural areas that have wooded areas that can produce 3-4 cords of deadwood every season. Therefore, there is a significant cost for wood for most homeowners.

I therefore believe that in this instance, which cannot be applied to every home, the cost savings were primarily in doing things yourself - cutting and managing wood and stove, managing the solar gain from the greenhouse, etc.

What I do like about the way they did things is that it was done with every-day materials and had a layering of systems and sources. I think this is a great way to augment and supplement heating systems and costs. The gravel/water subfloor thermal mass is a great idea. Every home should have one as part of their construction.

Personally, I believe a ground water heating system would have been similarly energy-saving, but at increased initial cost (well drilling). If you have a forced-hot-air heating system, however, a groundwater heating system may be fairly cost-effective in the long run to retrofit into your heating system, while providing both heating and cooling functions using the good old earth as the heat thermal mass and groundwater as the means to move that heat around.

As always, the trade-off seems to be what you're willing to do yourself, manual vs. automatic, etc.

Just my 2 cents. :)
A coworker of mine used a wood burning furnace for "efficiency". Most every lunch, he spoke of spending hours per day getting wood, transporting, splitting, drying, stacking, feeding, cleaning the furnace, etc. Definately not efficient in my terms.
My geothermal system I think is a realistic balance between increased installation cost, increased maintenance and energy savings ($) compared to the typical propane heat in my area. I am fortunate to live on a lake where the 32 degree water can be discarded, and have a 3/4 hp well for the source of the 45 degree water (open loop).
I had the luxury of designing my home and incorporated many 'green' ideas . . . some have not been fully implemented yet, but the basics are in place for the future . . .

. . . good insulation and a tight construction (low air-infiltration) are more common these days so I'm about average for new houses in this dept. . . .

. . . the house is set facing south, with about 75% of the window area on this side, engineered overhangs and deciduous trees keep them in the shade during the hot summer months. . . the attached garage's roof, also south facing, is set at the optimal angle for my latitude, and will eventually be fit out with hydronic solar panels . . .

. . . I have slab on grade for all ground level areas (no basement) with hydronic radiant heat (plastic tube burried in the concrete) . . . upper, framed floors have the same tube run between the joists . . . the good thing here is that the water temp required for this type of heating is 130"F or so . . . easily attained with solar panels . . . right now the heat is generated via a 60gal propane fired water heater . . .

. . . if it stays above freezing overnight and is at least partialy sunny with a high temp over 45"F the place heats itself . . . a bit cool in the morning, around 65"F or so, but the setpoint is only 68"F . . . on real sunny days it'll get up to around 75"F in the afternoon . . . if I leave the heat on on these days the place will overheat . . . the concrete slab really holds the heat . . . so far for this month I've had my heat off more days/nights than it's been on . . . I'm about 75 miles north of NYC . . .

. . . eventually, with the hot water panels mounted (waiting for bigger tax incentives) and supplying both DHW and heat for the floors I hope to cut my propane usage in half . . . but this might be a bit optimistc here in the northeast . . .

. . . cooling season is short here (~600hrs), so I have standard 12 SEER split system A/C . . . but heard an idea about running well water thru the floors in the summer to reduce the load (essentially open loop geothermal) . . . might try that this season . . .

overall, I think that it's many small things that will provide substantial reduction in heating/cooling costs . . . not a one-minded approach to some 'super-system' . . .

Pete C

here's a link for the company that I got my radiant heat supplies from . . . Radiantec . . . they have a write up on solar applications as well . . . I am not finacially involed with them in anyway . . .
Pete, similar situation for my house.
I used foam form walls for my lower level. They are 9 inch thick of concrete filled foam forms for great insulation and sound control. I also put these blocks around my theater room for sound insulation from rest of lower level. Also, I put acoustic cloth stretched on wooden frames as the interiour treatment which also took advantage of the acoustic properties of the foam wall. Looks great too!

Underneath the slab are (bottom to top) pea stone (drainage), plastic sheeting (moisture control), 2 inch foam insulation panels, wire mech (concrete strength plus something to tie the radiant pipes to), radiant pipes (still not connected, but there when I have a spare week), 4 inch concrete which the pipes are pulled up into during the pour (just below surface).

Walls are 2x6 w/ cellulose fill. Ceiling is 12 inch cellulose fill. Windows are argon filled & tinted.

Outside is Tyvek wrapped and cedar T&G.

When the wind is howling, a candle doesn't budge inside.

The house is nestled in 125 ft trees so very cool in the summer.

Combined with the geothermal, excellent energy control.
This is turning out to be an interesting thread (nice change of pace ;) ).

That's a pretty nice setup Pete.

Here in Las Vegas, Air Conditioning (Power) is our biggest utility expense. Since we have low humidity a lot of people use swamp coolers, but it will not achieve a desired differential in temperature reduction for the primary cooling means.

At my old house I did make a "pre-cooler" for our AC compressor unit so the air was "cooled" via a swamp cooler pad before it entered the coils of the compressor. This reduced the cooling effort for the unit, thus reducing the amount of current it will draw.

I just cut a square piece of plywood and placed it over the top of the unit. It was large enough so there was overhang on the sides. I cut a hole in the center for the fan.

I then attached two by four legs on the four corners, then placed swamp cooler pads on the four side faces (to the legs). I then placed PVC pipe around the bottom part of the plywood where the swamp cooler pad (thickness) met with this plywood.

I then placed spray paint nozzels in the PVC and pointed them down so they would spray on the top thickness of the swamp cooler pads. The PVC was then attached to a water source via a solenoid valve and 1/8" needle valve.

The solenoid valve was then connected to the compressors relay coil (same 24 VAC can trip the solenoid) so the water would only come on when the unit was on.

Now when the unit turned on the solenoid would open and water would trickle down the swamp cooler pads. The fan of the compressor would draw the air through the pads (cooling the air) then to the coils.

I adjusted the needle valve so maximum cooling was achieved with minimal water use.

Couple of downsides was the water just went on the ground, but it used so little I never noticed any increase in my water bill. Also you have to make sure the pads are far enough away from the coils to prevent any possible water droplets from getting to them.

Also, this would only work in areas of low humidity (don't know the cut-off spec).

Rough (and I mean rough) pic below.

I may do this for our new house (two compressor units) as Nevada Power Company is getting ready to screw us again with price increases :angry: .


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evaporative cooling (swamp coolers) will work almost anywhere but are cost pohibitive for residential applications at current energy prices in places with high humidity (ie: you don't recoup additional investment costs in savings gained) . . . but as energy prices go up, these systems will be more attractive . . .

. . . many commercial/industrial cooling installations, even here in the high humidity of the northeast, use this technology . . .

. . . if water use is an issue, you could collect the run off from the swamp cooler pads and either re-circ it (back thru the cooler pad) or use it to water the lawn . . .

. . . not sure why you can't get your coils wet out west . . . I use my A/C all the time when it's raining and never had an issue ? ? ?

. . . my compressor is on the north side of the house, in the shade, to reduce some of the load. . . but, since I have a well and the only cost would be to pump the water, I might try this . . . do you have a link to one of these "swamp cooler pads" . . .

Pete C
I just went down to Home Depot and purchased the swamp cooler pads (they stock them here). There are many new types that came out since I did this I believe.

As far as water on the coils, I felt that it was to easy to prevent the coils from getting exposed to the water by moving the pads out a little, so why not do it.

One thing I did remember doing was connecting an inductive current meter to one of the 220 VAC legs to the compresssor and watched the current draw of the compressor. I then saturated the pads with water with my garden hose and noted the reduction in current. I then let the system run as normal, adjusting the needle valve until I reached this maximum current reduction. This is how I was able to achieve the maximum current reduction using the least amount of water.

Recirculating the water would be a pain as you would have to build a collection system, design in a circulating pump and a float so the pump would only turn on when a minimum amount of water was in the collection bin.

Although you may want to explore that option as the cost of running a small circ pump would be better than your well's pump.
was out researching this on the net and found a water-cooled condenser . . . so maybe I could just spray cold water directly on the condenser coils like they do . . . after all, these are outdoor units . . .

. . . they claim to have engineered the coil to heavier duty specs to avoid corrosion . . . but coils are aluminum and copper . . . neither of which corrode very fast (as long as you keep the salt/chemicals away) . . . my well water should be fine as long as I tap into it before my water softener . . .

. . . when summer hits, I'll borrow an amp meter and check it out using a garden hose . . . before I design and install anything extravagant . . .

Pete C
BraveSirRobbin said:
Recirculating the water would be a pain as you would have to build a collection system, design in a circulating pump and a float so the pump would only turn on when a minimum amount of water was in the collection bin.

Although you may want to explore that option as the cost of running a small circ pump would be better than your well's pump.
. . . this could be done easily with a sheetmetal pan and condensate pump (like what would be installed when the A/C air handler's condensate can't be pitched to drain) for less than $100 . . .

Pete C
Yes, just look up "swamp cooler parts" in Google for floats and pumps that could be used. Also be aware if doing this it is a good idea to automatically drain the pan and have it refill to prevent mold (periodically refresh the water supply).

Hmm, this thread sort of has me wanting to do this again. :angry:
Well, I may as well chime in more of my thoughts here, too. I purchased my current home in September 2005 with an eye toward installing geothermal groundwater heat pump system. It has some passive solar amenities - 6" outer construction, built on a small hill sloping to the south, facing southwest I have large windows and an overlapped "shed roof" style with windows at the top that can be opened for ventilation. All windows are crank-out casement style with capture locks and weather seals, double-pane with argon and tinting. House wrap, good insulation, double-thick roof insulation (I have vaulted ceilings).

I have a concrete foundation with crawlspace under the house, which could be made into a thermal storage area with a little work. Alas, the house has baseboard hot water (oil boiler) heating today, but I would rather have forced hot air simply because it would be as costly to replace the current baseboard with geothermal-compatible baseboards, and forced air allows use of air conditioning as well as heating.

The house is very tight. On calm days with full sun in the winter, with outside temps in the 20's F, the internal temps would maintain 65-70 degrees. On windy days, I figure mostly due to my fireplace flue not closing fully, it would not stay as warm. The front roof is also set at the proper angles for good solar water heating, so when I can afford it, that'll be an option. Trees are mostly cedars, with some evergreens and deciduous to thicken up and shade things in the summer.

Alas, this area has groundwater contamination that has been determined to be hazardous and so the EPA has declared no wells may be used or drilled for at least 100 years. They put in a water distribution system from the next ridge's aquifer. The pro is the water is free, but the con is my dream of geothermal heating here is a bust. I knew about the contamination when I bought the house, but was unable to get a determination about geothermal use before I bought it. So I'm looking at other ways.

I believe going solar as much as possible, along with maybe moving to on-demand water and heating using gas, may allow me to run more efficiently and at lower (??) costs. I have to work with an HVAC company and crunch the numbers more, of course.

The floors here are not yet finished, so there is the possibility of doing something hydronic with them. The other issues are ways to reduce electricity usage. I'm into HA, as you all know, and computers, and all things gadget-like. Most of those run on electricity. So I'm looking at ways to try to reduce that consumption as well.

Fun fun!
that contamination issue also is for non drinking water usage? You just pump it up, pull the heat out and send it back to the ground.
huggy59 said:
I would rather have forced hot air simply because it would be as costly to replace the current baseboard with geothermal-compatible baseboards, and forced air allows use of air conditioning as well as heating.
You would prefer hot air . . . IMHO, your nuts . . . I would never recommend a hot air heat system . . . and I do ductwork for a living . . .

I hate the stratification, the overly dry air, the drafts, even the dusty smell of the hot air . . .

. . . but as a cost effective solution when installing heat and A/C, they do have a place . . .

onto the matter at hand . . .

. . . with your vaulted ceilings and hot air heat, stratification would be even worse than normal, leaving you with cold floors . . .

. . . not sure what could be in the water that would precude it's use for geothermal, but bureacracy is a pain . . . I wanted to use a frost-proof shallow foundation when I built my home . . . but unless I paid a engineer to design and stamp it the local building dept. wouldn't approve it, and I even got a funny look when I talked to an engineer about it . . . two years later and they're in the building code for anyone to use easily . . . (they've been in use in europe for over 20 years)

. . . is there any reason you can't use the water you do have in an open loop system . . .

. . . also, the price of copper is up . . . you could get a quite a few dollars for your scrapped baseboard . . .

Pete C
pete said:
. . . not sure why you can't get your coils wet out west . . . I use my A/C all the time when it's raining and never had an issue ? ? ?
The best reason is to prevent build-up of scale in the condenser. This scale reduce the condenser's heat transfer capacity and thus, the system's overall efficiency.

The effect that water evaporation has on the surface of your swamp cooler and evaporator is the same as the one in an industrial Cooling Tower. Here is an explanation.

There as several companies that live out of water treatment for (among other things) cooling towers. Some companies use cheap chromate which is toxic (see here ), but NAPCO per instance uses phosphates (see here ).