Inefficient home or inefficient GSHP?

[mechanic]

Interesting mikesolar, I'll have to look into that

[mechanic]

Oh and that register in the bathroom is well inside the insulated area, they all are.

[JRMichler]

I just ran across this thread. I built a house 12 years ago. Calculated heat loss was 13,000 BTUH at 70 deg F inside and -20 F outside for 1320 square feet. It was built on a crawlspace, with the crawlspace walls insulated R20, but no insulation in the floor.

I noticed the heating system was running more than it should, so I measured the heat loss at 18,000 BTUH. THEN I got hold of a copy of ASHRAE Handbook of Fundamentals and found the section on basement floors. The estimated heat loss through the floor was almost 5,000 BTUH.

I also had trouble with the heater cycling several times per hour. Turned out that the electronic thermostat was designed to cycle five times per hour. It only changed the percentage of run time. I finally found a thermostat that cycled on and off based only on temperature. Now it runs for an hour or two and shuts off for a half hour or more on cold days. I do not feel the temperature variation when it's less than 1.5 deg F or so.

[AC_Hacker]

Originally Posted by JRMichler

I just ran across this thread. I built a house 12 years ago. Calculated heat loss was 13,000 BTUH at 70 deg F inside and -20 F outside for 1320 square feet. It was built on a crawlspace, with the crawlspace walls insulated R20, but no insulation in the floor.

I noticed the heating system was running more than it should, so I measured the heat loss at 18,000 BTUH. THEN I got hold of a copy of ASHRAE Handbook of Fundamentals and found the section on basement floors. The estimated heat loss through the floor was almost 5,000 BTUH.

I also had trouble with the heater cycling several times per hour. Turned out that the electronic thermostat was designed to cycle five times per hour. It only changed the percentage of run time. I finally found a thermostat that cycled on and off based only on temperature. Now it runs for an hour or two and shuts off for a half hour or more on cold days. I do not feel the temperature variation when it's less than 1.5 deg F or so.

Wow! Looks like your math was just about right.

I did some underfloor insulation under my kitchen floor. I don't have the numbers like you do, but prior to the insulation, on cold winter nights, my floor measured a degree more than the crawlspace temperature. Now, with the insulation in (my scheme is 50% complete), on cold winter nights, the floor measures about a degree less than average kitchen temperature.

Do you have a solution for your floor?

-AC

[Mikesolar]

Speaking of underfloor heating not being as well insulated as it should be, I once did a solar pool heater to replace gas heaters that were only lasting 3-4 years each. The owner had high gas bills and thought the solar would help. I put in a system that was sized right for the pool area but it wouldn't heat. I added a couple more panels. Still not enough heat.

Turns out there was an aquifer running under the pool and sucking out all the heat. Live an learn. Point is, when I first started doing floor heating, I was trying to get people to put 1.5" of SM under the floor, then it was 2", now it is 4"+ if possible ( code in the UK, I'm told) and the passivhaus is 6". Heat loss is dT x U value x area. JR, Maybe you can get an opening to the crawlspace and get some SM on the floor. Do a world of good.

[AC_Hacker]

Originally Posted by Mikesolar

...I was trying to get people to put 1.5" of SM under the floor, then it was 2", now it is 4"+ if possible ( code in the UK, I'm told) and the passivhaus is 6"...

I had to go to the Internet to find out what "SM" was.

Are you recommending SM foam (AKA: "blue foam"), rather than white foam because of it's better R-value? I see that it is strongly recommended for applications where a foam insulation would come in direct contact with water, such as exterior foundation insulation, etc.

-AC

[JRMichler]

Originally Posted by Mikesolar

JR, Maybe you can get an opening to the crawlspace and get some SM on the floor. Do a world of good.

The crawlspace is accessible. If I added insulation, it would still have the concrete foundation walls conducting heat down to the concrete footings. The insulation would be only partly effective. Then I would need a way to fireproof it.

My (near) future retirement home was just finished about two years ago. Same size, similar insulation, but the crawlspace has four inches of XPS (extruded polystyrene) insulation. Vapor barrier on the bottom, then the foam, then two to three inches of sand on top for fire resistance. The total calculated and measured heat loss is about 13,000 BTUH.

[Mikesolar]

Originally Posted by AC_Hacker

I had to go to the Internet to find out what "SM" was.

Are you recommending SM foam (AKA: "blue foam"), rather than white foam because of it's better R-value? I see that it is strongly recommended for applications where a foam insulation would come in direct contact with water, such as exterior foundation insulation, etc.

-AC

Yes, white foam (EPS) comes in 3 different densities (here in North America), Type 1, 2, and 3 (there may be others). Type 1 should be used for nothing but packaging material and is useless as a home insulation although it is still sold as such. Type 2 is a higher density and is usually tinted green or blue and is suitable for walls (Plastifab is one brand) under stucco. Type 3 is hard to get but is suitable for under slab.

SM (XPS) is just a trademark of Dow. Celfort sells the same thing in a pink board. The extruded polystyrene has only one density that I know about (R5/in) and is traditionally used under inverter roofs and underslab but has a much higher GHG content in its manufacture than EPS so people want to use the EPS (it is also cheaper/ Rvalue)

[skyking]

I did the dig for my brothers geothermal.
http://ecorenovator.org/forum/geothe...m-install.html
He has a couple of vacuum tube solar collectors on a separate loop with heat exchangers. He can take the peak summer solar heat and put it into the ground for storage. Maybe you can do something along those lines?
His first year in there he was not that thrilled with his heat, his ground got cold too. Turns out he uses very little AC so he puts no heat in that way, and he was way late on trying to push heat in with the solar. This year he will aggressively heat the ground heat sink starting in late July.

[AC_Hacker]

Originally Posted by skyking

I did the dig for my brothers geothermal.
http://ecorenovator.org/forum/geothe...m-install.html
He has a couple of vacuum tube solar collectors on a separate loop with heat exchangers. He can take the peak summer solar heat and put it into the ground for storage. Maybe you can do something along those lines?
His first year in there he was not that thrilled with his heat, his ground got cold too. Turns out he uses very little AC so he puts no heat in that way, and he was way late on trying to push heat in with the solar. This year he will aggressively heat the ground heat sink starting in late July.

Where in Western Washington is your brother's GSHP install?... What is his ZIP CODE?

When he did a heat load analysis on his house, what were the results?

How many feet of pipe are in the ground?


-AC