Greetings Home Energy Community,

 

Excited about joining. I just found out GBA published my Cost-Effective Passive Solar Design article. I love feedback especially the critical type. Iam also interested in any other tricks out there that could save construction costs and boost performance for passive solar design. 

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Overall the article raises the right issues and addresses them well. Some other points:

 I've found on my ICF passive solar house in central Minnesota after four heating seasons that high efficiency triple glazed windows are the best money I spent on the house. They do the same thing that mass storage does. Less radiation comes in though 3 panes but half as much goes out at night limiting the temperature swings just like thermal mass.

South facing glazing = 356 ft2. Space heated area = 2497ft2. Ratio = 14.3%. (this is not rough opening but actual glass area.)

On cold sunny periods from -10 F night to+10F day I get from about 58 to 60 Fin early morning to 68 to 70 late day.

I let the lower level fluctuate from 50 to 60 since were not down there much.

The thermal mass I do have besides the building materials is 2 inches of gypcrete on upper floor for radiant floor heat and the lower level slab. I would not spend the money for radiant floor if I were to build again because thermostat setback is difficult, the pumps use as much as an ECM blower for forced air, I needed force air for air conditioning anyway,the geothermal system does not work as well for hydronic heating even low temp radiant floor. It also makes floor coverings a challenge due to insulative wood,cork, or carpet. But I would consider the gypcrete for thermal mass alone.

I think the ICF construction with 2.5 in. foam inside and 4.5 on outside of concrete does contribute a little to thermal mass. Some day I will plant a T/C against the concrete wall and data log the temperature swings.

Overhangs are less than ideal because of the achitecture and due limit fall and spring radiation. Geothermal cooling is so efficient in this neck of the woods that late summer radiation is not a big factor.

The house has too much east,west and north glass at 129 ft2 but I think it totally eliminates glare. The triple glaze might help glare a little to. We seem to have very little bleaching of wood or fabric, I think also due to triple glaze - and no condensation at any temperature. Too many of the windows are operable but some days the extra ventilation is great. These Canadian operable were a little more than non, but with the double gasket and good hardware I have not notices any difference in infiltration due to more or less condensation on the windows. I've learned other interesting things but enough for now. Hope this helps.

Leo

Thats really good to hear about the triple panes. It seems like I hear it both ways as to their cost-effectiveness. They are really tough to justify in my part of NC.  What brand did you use and do you happen to know the SHGC?

 

You suggest what many have been finding with the issues of radiant in highly efficient homes. Very interesting. I have a project Iam pricing now where the client wants both radiant and Geo. Iam intrigued by your comment suggesting Geo is not good for radiant. We are looking at using the new Bosch geo line and addressing the radiant heat with its own water to water compressor. The Bosch folks are saying this unit will handle over 95% of the heat load.

ORNL has done the most research of the benefits of Thermal mass  You may or may not want to duplicate their efforts. They found the ICF mass of little benefit.

The Canadian manufactures are the best I found. They are pulltruded fiber glass from Fibretech in Ontario. Check there web site for specs. Accurate Dorwin of Winnipeg was my second choice.

Well radiant will certainly work with geo. But be aware of what the maximum output temperature for water is. It works better if left on 24/7 because of high mass floor it will take a while to get to temp if set back when occupants leave. Works better with non insulative floor covering and that you have enough tubing in the floor to transfer the output of the geo unit at it's output temperature. The Geocomfort unit required a buffer tank and I didn't like the geo unit running to keep it at 115 F or so if the thermostats were not calling for heat during a sunny period.

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