Geothermal

[ericjeeper]

I believe some utilities will also give you a break on your electric bill as well. Mass Electric used to, not sure if they still do since being swallowed by National Grid.

I love the idea of passive solar... probably not the kind you mean... just big arse south, east and west facing windows.

Unfortunately, and hopefully without getting too political here, the $1500 tax credit, which one can get for replacement windows, stipulates a solar heat gain coefficient of 0.30 or less... no matter where you are in the country. A low SHGC is great if you spend the majority of the time cooling. Unfortunately, for this small part of the country (y'know, the entire northern half) the primary heats and doesn't even have AC, save for maybe a window unit... maximizing SHGC while minimizing U-factor makes the most sense. Looks like I'll be getting my $1500 on the new boiler, and not on windows.

Unfortunately The SHGC and the U factor run sort of hand in hand.
It usually takes two layers of Double lo-e to achieve a low number.
But here is my take on solar heat gain.. Ok lets say that clear southern facing window lets in 100,000 btus during the six hours of sun that shine on it.. We still have 18 hours when the sun is not hitting it..Then if it is just a clear non insulated glass pack it will possibly dump out many times more than it collected.
A prime example is my hydronic solar collectors. I can force them to run 24 hours a day. So during the sunny part of the day they will bring my six hundred gallon tank up to 140 degrees.Now if I let the pump run round the clock. It will dump all that stored energy back out the panels.
So the best possible scenario for a window is a clear pack during the sunny part of the day, Then all the sudden its features change to an insulated glass pack. LOL Which for now is impossible..
So we have to pick our battles.. And I choose to forfeit a big solar gain and opt for a higher insulation value.
I have radiant heat in my slab. My bedroom has 2 double hungs facing south. with lo e and argon.the numbers on them are roughly u factor of .34 and SHGC of 35 They kind of screw me with my heat type. They will let a fair amount of sunshine/heat in during a few hours of the day., So that satisfies my thermostat in the bedroom. (Which in turn will turn off the floor loop.). Ok now evening settles in the heat which came in the double hungs will slowly go back out and the loop will come on and try to play catch up.
I have one other window in that room.an inline slider it is 67 inches wide and 48 tall. with a triple with krypton and double soft coat lo e.At night at 15 degrees exterior temps. The two different glass types will vary on inside surface temps as much as 8 degrees.Of course the triple with krypton is the warmest. The numbers on it is . u factor .18 SHGC is .26
I only have 4 windows left in the house to replace with triple with Krypton.I plan to replace these four this summer. (My house is not even 5 years old yet.)Will the triple ever pay for itself? Maybe not in actual dollars but for sure in comfort. My office window is double with argon. And My chair is less than 3 feet from it.. when it is cold outside I can barely stand to sit here.The cold just radiates through it to the point it feels like cold air rushing in.Yet it is virtually air tight. Ok if this makes any sense at all..

 

[Moss Man]

You are spot on about picking our battles. In a true passive solar home you need to address the heat loss back out through the larger windows at night and that runs into more cash layout for insulated window covering of some type. If you have interior shutters and close them at night, the thermal mass in the sloar gain area of the house will easily release enough heat to keep the house warm enough to sleep in. I have a semi-passive solar house and there alot of days in mid-winter that we let the wood fire go out at noon and we don't fire it back up until the next morning. Cloudy days are a different story all together.

Striking a balance can be real hard to achieve when it comes to optimum performance of a home. Insulation and air tightness are key and then energy becomes much cheaper to address.

 

[ihookem]

I just don't get geothermal. Can anyone explain how I can take 55 degree water and warm my house to 70 degrees? I have heard you pump water into a compressor and it warms it up, but doesn't it take as much energy to warm the water as it does to heat it with gas? I don't get it! I can see how it would cool but not when it comes to heat.

 

[atlarge54]

I just don't get geothermal. Can anyone explain how I can take 55 degree water and warm my house to 70 degrees? I have heard you pump water into a compressor and it warms it up, but doesn't it take as much energy to warm the water as it does to heat it with gas? I don't get it! I can see how it would cool but not when it comes to heat.

Have you ever noticed how warm the floor is in front of your refrigerator? That heat came from an area that was far cooler than 50 degrees. I guess maybe you need to understand how large amounts of energy can be transfered when a "phase change" liquid to gas and back occurs.

 

[Marc]

Unfortunately The SHGC and the U factor run sort of hand in hand.
It usually takes two layers of Double lo-e to achieve a low number.
But here is my take on solar heat gain.. Ok lets say that clear southern facing window lets in 100,000 btus during the six hours of sun that shine on it.. We still have 18 hours when the sun is not hitting it..Then if it is just a clear non insulated glass pack it will possibly dump out many times more than it collected.
A prime example is my hydronic solar collectors. I can force them to run 24 hours a day. So during the sunny part of the day they will bring my six hundred gallon tank up to 140 degrees.Now if I let the pump run round the clock. It will dump all that stored energy back out the panels.
So the best possible scenario for a window is a clear pack during the sunny part of the day, Then all the sudden its features change to an insulated glass pack. LOL Which for now is impossible..
So we have to pick our battles.. And I choose to forfeit a big solar gain and opt for a higher insulation value.
I have radiant heat in my slab. My bedroom has 2 double hungs facing south. with lo e and argon.the numbers on them are roughly u factor of .34 and SHGC of 35 They kind of screw me with my heat type. They will let a fair amount of sunshine/heat in during a few hours of the day., So that satisfies my thermostat in the bedroom. (Which in turn will turn off the floor loop.). Ok now evening settles in the heat which came in the double hungs will slowly go back out and the loop will come on and try to play catch up.
I have one other window in that room.an inline slider it is 67 inches wide and 48 tall. with a triple with krypton and double soft coat lo e.At night at 15 degrees exterior temps. The two different glass types will vary on inside surface temps as much as 8 degrees.Of course the triple with krypton is the warmest. The numbers on it is . u factor .18 SHGC is .26
I only have 4 windows left in the house to replace with triple with Krypton.I plan to replace these four this summer. (My house is not even 5 years old yet.)Will the triple ever pay for itself? Maybe not in actual dollars but for sure in comfort. My office window is double with argon. And My chair is less than 3 feet from it.. when it is cold outside I can barely stand to sit here.The cold just radiates through it to the point it feels like cold air rushing in.Yet it is virtually air tight. Ok if this makes any sense at all..

Well, they don't quite go hand in hand, but I think the window companies want you to think that. As a matter of fact I'm having good luck with Canadian companies in my search for windows for my farmhouse that have low u-factor and high shgc. Accurate Dorwin, Fibertec and Inline Fiberglass all have a double hung, hard coat low-e with a u-factor in the mid .20's and a shgc in the mid .40's.

It's the low e coating that makes all the difference. Most of the soft coats, from what I've seen, are to infrared reflective.

If you look at a solar irradiance chart, like this one-

http://en.wikipedia.org/wiki/File:Solar_Spectrum.png

you'll see a vast majority of the available energy is in the visible and short wavelength infrared, or what is referred to as 'near infrared.'

Opaque solids such that you'd find in the average house radiate primarily in the far infrared range (long wavelength infrared). The hard coatings tend to be reflective in the far infrared only, whereas the soft coatings are more or less evenly reflective over the whole infrared range (depending on the combination used).

For a primarily heated enclosure, the optimal coating is one that reflects all far infrared and transmits all near infrared and visible... so you still transmit a lot of solar during the day, and all of the infrared radiated by objects in the house is reflected because that's all far infrared.

Check out the efficient windows collaborative webpage, this list is for the most energy efficient windows for my area-

http://www.efficientwindows.org/city_all.cfm?new=E&prodtype=WN&id=17

The first type on the list is low u-factor, high shgc triple glazed, and the second is low u-factor, high shgc double glazed. As a matter of fact, according to this list, low u-factor/low shgc triple glazed is only fourth most cost effective, and this is the type of window that a lot of the majors have been trying to sell me on, all because it meets the stimulus package criteria (Harvey, Marvin, Newpro, Andersen which is double pane, Pella, and a few others I looked at).

Fortunately for me, I'll be earning my $1500 credit via a new boiler this year so I won't have to worry about getting it from the windows. Instead I'll probably end up buying from one of those Canadian companies and putting the double glazed on the E, W and S facing aspects and triple glazed on the N (house gets a lot of sun).

It's stupid the tax credit requirements impose a shgc of .30 or less, when to get an energy star rating for the northern zone that's primarily heating, there is no requirement for shgc, only for a u-factor of .30 or less.

 

[HorseShoeInFork]

I think folks who have or will have geothermal hvac equipment will come out big time ahead over the next 20 years. I think we (USA) are setting ourselves up to see electricity costs do what oil prices have done in the past 7 years.

 

[Marc]

I just don't get geothermal. Can anyone explain how I can take 55 degree water and warm my house to 70 degrees? I have heard you pump water into a compressor and it warms it up, but doesn't it take as much energy to warm the water as it does to heat it with gas? I don't get it! I can see how it would cool but not when it comes to heat.

You're confusing temperature with heat. Two related, but separate concepts. Heat is the statistical measurement of the available thermal energy in a given mass. The heat source for a ground source heat pump is the ground. Being that the ground has quite a bit of mass, there's a tremendous amount of available energy.

Despite the fact the distributed intensity of the heat, which really is what temperature is measuring, is low compared to what it is in a house (55 deg vs 70), if you input work into the system, you can get heat to flow to the house.

Think of it as taking energy from a large mass at low temperature and consolidating it into a smaller mass. Smaller mass, same overall amount of energy, and the temperature must rise. But you need work to do that, which is why the compressor is there.

Mechanically speaking, a heat pump cycle is the mirror opposite of a refrigeration cycle.

The working fluid in the system is typically something that has a low boiling point, in the temperature range and pressure the system is working with.

So the four key parts are the evaporator, compressor, condenser and expansion valve. The working fluid enters the evaporator at low pressure in a liquid/vapor mixed phase. As it continues evaporating because of the pressure drop, it must absorb energy to break the intermolecular forces that keep it a liquid (known as the latent heat of vaporization).

The gas is about the same temperature as the ground (which yields it heat to the condenser) as it goes to the compressor. The compressor uses energy to raise the pressure of the gas (which requires work) to force it back to liquid phase, in the condenser. This raises the temperature of the fluid, because the particles must yield energy to settle back down to a liquid phase and recreate the intermolecular bonds. If the system is design right, the temperature increase will surpass not only the ground temperature, but the inside temperature as well. This heat is then extracted and delivered to the house while the liquid moves onto the expansion valve.

Here is where it decreases in pressure by being forced through a very small cross sectional chamber, forcing some of it to turn to gas again and the cycle restarts.

Same thing happens in reverse in your refrigerator or an air conditioner.

Don't know if any of that makes sense.


Similar phenomena occur on other places that might help you understand the components of the system. If you've ever release a compressed gas from a cylinder at a high flowrate, you'll notice it makes everything cold. Even though the compressed gas in the cylinder was the same temperature as the surrounding environment, when it is released and it expands (pressure drops) it absorbs heat energy from its environs and causes a temperature drop. This is like the expansion valve/evaporator side of the heat pump.

Similarly, air compressors need cooling, because compressing air forces the molecules closer together. This lowers the energy in the bonds between them so they must liberate heat and therefore heat up their surroundings quite readily. This is like the compressor/condenser side of the heat pump.

 

[blis]

I just don't get geothermal. Can anyone explain how I can take 55 degree water and warm my house to 70 degrees? I have heard you pump water into a compressor and it warms it up, but doesn't it take as much energy to warm the water as it does to heat it with gas? I don't get it! I can see how it would cool but not when it comes to heat.

Its easiest to think it as refrigerator that works backwards. Refrigerator cools the space inside it, geothermal heatpump heats the area around it...

 

[ericjeeper]

Well, they don't quite go hand in hand, but I think the window companies want you to think that. As a matter of fact I'm having good luck with Canadian companies in my search for windows for my farmhouse that have low u-factor and high shgc. Accurate Dorwin, Fibertec and Inline Fiberglass all have a double hung, hard coat low-e with a u-factor in the mid .20's and a shgc in the mid .40's.

It's the low e coating that makes all the difference. Most of the soft coats, from what I've seen, are to infrared reflective.

If you look at a solar irradiance chart, like this one-

http://en.wikipedia.org/wiki/File:Solar_Spectrum.png

you'll see a vast majority of the available energy is in the visible and short wavelength infrared, or what is referred to as 'near infrared.'

Opaque solids such that you'd find in the average house radiate primarily in the far infrared range (long wavelength infrared). The hard coatings tend to be reflective in the far infrared only, whereas the soft coatings are more or less evenly reflective over the whole infrared range (depending on the combination used).

For a primarily heated enclosure, the optimal coating is one that reflects all far infrared and transmits all near infrared and visible... so you still transmit a lot of solar during the day, and all of the infrared radiated by objects in the house is reflected because that's all far infrared.

Check out the efficient windows collaborative webpage, this list is for the most energy efficient windows for my area-

http://www.efficientwindows.org/city_all.cfm?new=E&prodtype=WN&id=17

The first type on the list is low u-factor, high shgc triple glazed, and the second is low u-factor, high shgc double glazed. As a matter of fact, according to this list, low u-factor/low shgc triple glazed is only fourth most cost effective, and this is the type of window that a lot of the majors have been trying to sell me on, all because it meets the stimulus package criteria (Harvey, Marvin, Newpro, Andersen which is double pane, Pella, and a few others I looked at).

Fortunately for me, I'll be earning my $1500 credit via a new boiler this year so I won't have to worry about getting it from the windows. Instead I'll probably end up buying from one of those Canadian companies and putting the double glazed on the E, W and S facing aspects and triple glazed on the N (house gets a lot of sun).

It's stupid the tax credit requirements impose a shgc of .30 or less, when to get an energy star rating for the northern zone that's primarily heating, there is no requirement for shgc, only for a u-factor of .30 or less.

I still say we have more darkness and cloudy days than we do bright sunny days.
I am a firm believer in low u-factor windows. I prefer soft coat lo e as the application 99% of the time is a better appearance on the glass.. Hard coat will often have streaks in the glass.
If you do choose to purchase varying U factor windows please be sure to keep us informed what the interior glass temps are at night when it is very cold out. I have the current setup you are considering now.. basically.. double panes on the south. But triples everywhere else.No north facing windows at all, minus two in the garage overheads.. Like I said in other post.. My south side double panes will be replaced this year..With triple with krypton, super spacer premium between the glass.

 

[John D]

Problem here with geo-thermal is the price of electricity has skyrocketed since oil hot $140+ a barrel last yr,and hasnt come down one cent since.I can't see any reason to go that route with the electric rates we are paying without substantial rebates and incentives.You'd need to do a grid tied solar system as well,and if you combine the cost of a geo-thermal, and grid tied system,your looking at 100K dollars for a good sized house,but you'd be energy independent for the most part,mainteance ,and repairs aside.

 

[ihookem]

How much does it cost to run a heat pump for an avrerage geothermal unit? Again the heat comes from somewhere. Although refrigerators are only a dollar a week. Even at 20 dollars a week to use a geothermal pump wouldn't be so bad in the winter. One poster said 19 years for a payback, I just don't see it but we have to do something about energy. With solar it just seems the pay back is way too high. My neighbor looked into it and said his kids kids will thank him but they are junk by then. Honestly it's a little off the subject but I think a good gassifier for heat and hot water is the cheapest yet for getting your own energy, and that ain't cheap neither. One question though, how hard could it be to run water through some black pipes on south side of house, hook it up to the water heater somehow and let the sun heat the water? Then how hard would it be to just run air through black pipe like 4" pvc from inside the house in the basement, run air from the basement outside through the pipe encased in a glass room a foot wide so the pipe is between the glass and the house. The air warms up as it runs through and goes back into the house warm? A little off subject but has anyone tried this?

 

[AKKAMAAN]

How much does it cost to run a heat pump for an avrerage geothermal unit? Again the heat comes from somewhere. Although refrigerators are only a dollar a week. Even at 20 dollars a week to use a geothermal pump wouldn't be so bad in the winter. One poster said 19 years for a payback, I just don't see it but we have to do something about energy. With solar it just seems the pay back is way too high. My neighbor looked into it and said his kids kids will thank him but they are junk by then. Honestly it's a little off the subject but I think a good gassifier for heat and hot water is the cheapest yet for getting your own energy, and that ain't cheap neither. One question though, how hard could it be to run water through some black pipes on south side of house, hook it up to the water heater somehow and let the sun heat the water? Then how hard would it be to just run air through black pipe like 4" pvc from inside the house in the basement, run air from the basement outside through the pipe encased in a glass room a foot wide so the pipe is between the glass and the house. The air warms up as it runs through and goes back into the house warm? A little off subject but has anyone tried this?

Well, as I said in my earlier post...On a new construction.....insulation is the only investment that is maintenance free and last forever......

 

[ihookem]

Akkamann, you got it, and it's relatively cheap except for foam. I'm almost done with my home and I have 4"-5" of foam in the walls and 20" of cellulose in the ceiling with Anderson windows. I have the basement joist rim with 3" of foam too. But I just can't help looking for cheap heat and geo makes me think. I still say free wood is the cheapest. Later, ihookem.

 

[ericjeeper]

Akkamann, you got it, and it's relatively cheap except for foam. I'm almost done with my home and I have 4"-5" of foam in the walls and 20" of cellulose in the ceiling with Anderson windows. I have the basement joist rim with 3" of foam too. But I just can't help looking for cheap heat and geo makes me think. I still say free wood is the cheapest. Later, ihookem.

My neighbor is on his second Geothermal unit..
He says the lifetime on the units are about ten years.. If that is true.. Talk about a pee poor payback period.
You say you have Anderson windows.. Are they Casements?or double hung?
What are the numbers on them? Lo e and argon? if so that is tops an R 4. So all your spray foam is doing is bringing up the big numbers.. Concentrate on the little numbers. Doors and windows. Many windows achieve an R 10. Thats about as good as you can get.. That is until someone can make "aero-gel" Frozen smoke" totally clear.. Then look out.. The total home designs will change..

 

[John D]

I keep wondering if you could use a large geothermal ground loop,and just run a circulator and a large HX and get any sort of cool air for the summer,without the huge electrical expense of running a compressor.Around me the groud temps are 51 degrees.It seems 51-54 at the HX,if its a large unit,could get you high 50s out the ducts,that would work for all but the hottest days around here.I think the key is a very large HX.Just an idea Id like to try,but probably never will.
I wish I knew how much electricty the geo thermal setup would use per hour,I know running any sort of compressor and refrigerant to transfer heat is not cheap.

 

[ihookem]

Ericjeeper, I have casements in the living area and doubles hung in the bedrooms. I can't remember exactly what the numbers are but one is 34 or 32. I know Andersons aren't the very best but they are good. We are going to get some good blinds and shut them at night, this should help a bunch. I know the barely make the energy star ratings but didn't look into it yet. Later, ihookem. P.S, I can look at the numbers tomorrow .

 

[atlarge54]

My neighbor is on his second Geothermal unit..
He says the lifetime on the units are about ten years.. If that is true.. Talk about a pee poor payback period.
You say you have Anderson windows.. Are they Casements?or double hung?
What are the numbers on them? Lo e and argon? if so that is tops an R 4. So all your spray foam is doing is bringing up the big numbers.. Concentrate on the little numbers. Doors and windows. Many windows achieve an R 10. Thats about as good as you can get.. That is until someone can make "aero-gel" Frozen smoke" totally clear.. Then look out.. The total home designs will change..

Every glass shop I've talked to in the past few years has told me to avoid high performance glass. Loss of seal was the main problem, not a matter of if but when failure will occur. I purchased new Pellas over 20 years ago which had low e coating. I can't recall the advertised R value but it didn't take long to determine it had to be some phoney lab generated number. For the money spent I thought the overall quality was poor and will never buy another Pella product. I find it extremely difficult to believe any window can equal the R value of 2" of foam insulation. Does anyone have any real life experience with high performance glass? Not intending to hijack the Geothermal thread but windows are generally the big x-factor in an "easy to heat home". I know of two people with geothermal systems, both failed at 13 years of age.

 

[Marc]

My neighbor is on his second Geothermal unit..
He says the lifetime on the units are about ten years.. If that is true.. Talk about a pee poor payback period.
You say you have Anderson windows.. Are they Casements?or double hung?
What are the numbers on them? Lo e and argon? if so that is tops an R 4. So all your spray foam is doing is bringing up the big numbers.. Concentrate on the little numbers. Doors and windows. Many windows achieve an R 10. Thats about as good as you can get.. That is until someone can make "aero-gel" Frozen smoke" totally clear.. Then look out.. The total home designs will change..

There's already a company making mostly clear, aerogel insulated roof panels for solariums and such... sandwiched in polycarbonate. They're ridiculously expensive. And the gains to be had from insulating with aerogel I doubt will be enough to drive economies of scale for higher production... unless someone comes up with a way to produce it at much lower material and process cost.

There are also companies experimenting with vacuum insulated glass packs, which would theoretically be more efficient still, but the spacers to hold the panes apart still apparently look a little distracting. Plus there's the much greater challenge of seal failure too, but I think that maybe easier to figure out than a cheap way to get aerogel in there.

 

[blis]

Just wondering, what are normal u-values for windows over there? since over here they tend to be around .80-1.20 for normal quality windows...

 

[Marc]

Just wondering, what are normal u-values for windows over there? since over here they tend to be around .80-1.20 for normal quality windows...

U-factors are in imperial values over here (Btu/hr-sq ft-°F) rather than your much nicer and simpler metric (W/sq m-°C). Anyone know what the conversion factor is? I could figure it out, but damn I'm lazy...