Green Home Building and Sustainable Architecture

Sustainable architecture is an exciting and important field, with many people reviving traditional methods of building and others creating innovations to established practices. Kelly Hart, webmaster of the popular website www.greenhomebuilding.com, posts text and photos featuring what he discovers from around the world.

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Kelly Hart has been involved with green building concepts for much of his life. He has also worked in various fields of communication media, including still photography, cinematography, animation, video production and now website development. Kelly has lived in an earthbag/papercrete home that he built and consults about sustainable building design.

September 20, 2010

How Geothermal and Radiant Heat can Save Money and be More Comfortable

by guest blogger Pete Frank

There has been a lot of debate about which “sustainable” products are the best “value”. The answer to this question may be influenced by utility cost, natural resource availability, whether the building is new or preexisting, and the quality of the construction. The debate includes technologies like radiant floor heating, geothermal, photovoltaic (solar electric) and hydronic solar water heating systems (solar thermal), wind turbine technology, methane accumulators for septic systems and other biomass based energy collectors, etc. I am going to focus on what is the most prevalent “alternative” system for homes: geothermal and radiant heating systems. It seems that geothermal systems are the first building block that people are using with their sustainable houses.

At this point you may be thinking, “What is a geothermal heating system?” Geothermal heating systems use stored heat from the earth's crust in conjunction with heat pump technology to move and amplify heat instead of making heat. The crust of the earth maintains the average temperature of that location annually, usually between 42 and 75 degrees Fahrenheit. Now to clarify, I am not talking about active geothermal (often called geothermic) heating systems, like they have in Iceland and other areas where there is thermal activity right near the surface of the Earth's crust. Conventional geothermal is using latent heat stored in the crust of the Earth from the sun. Yes, I said it; the geothermal systems essentially use solar energy in conjunction with electricity to heat the house.

Why invest in geothermal? A geothermal system will save 50-75% of the heating bill per year (varies by utility rates), and in cooling it will be in the range of a 30-50% decrease in cooling costs. This turns into real money every year coming back to the buyer; we are talking thousands of dollars! The cost of a fully installed geothermal system can be $12,000 - $15,000 higher than a conventional heating and cooling system (vertical well systems will be higher, and it always depends on the size of the house). But when we talk about the return on this investment (ROI) we are generally in the range of 5-10 years. I have had instances where, based on the fuels available, my clients may come in at 3 years, but that is rare. From my research these systems have the most consistent ROI of any of the systems we deal with.

Geothermal systems are available in forced air or hydronic units, making them quite versatile for either a conventional forced air, ducted system or for use in a radiant floor heating system with forced air for cooling. Most people are familiar with forced air heating and cooling systems. Radiant is becoming more popular every year because it is typically about 30% more efficient as a delivery method when compared to forced air. The reasons for this are very easy to understand.

We have always learned that heat rises right? Well, yes and no. Hot air rises. Heat travels through convection, conduction, or radiation. If you are heating a room with forced air there is generally not a consistent temperature in that room. There are going to be warm spots and cold spots AND it will be warmest at the ceiling. With a radiant floor, there is more consistency in the heating because the “hot air” is not rising. You are heating the floor, which heats the objects in the room thus heating the space. Most of the heat is traveling via conduction and radiation and not convection (hot air rising). The heat is kept lower spatially, generally where the people are, and you can usually keep the room temperature lower and “feel” warmer because the heat is literally everywhere. It's a pretty easy concept. Radiant heating also incorporates the mass of the floor like a battery of stored energy. Although these systems are more expensive to install than forced air systems, people who have lived in a radiant house seldom build their next home without radiant. It is not about the money, it's about the comfort.

There are several different ways to put radiant heating into the floor. Tubing can go in concrete, a lighter gypcrete, over the floor with furring strips, or into a ready to lay product like The COMPLETE Radiant Panel (www.TheCompleteRadiantPanel.com) . All of these types of radiant systems are generally compatible with a geothermal system. The general rule is that if the tubing is above the subfloor, it can be used with an “alternative energy” system whether that is geothermal or solar thermal. (Of course, always consult design software or a professional to be sure that your radiant floor can keep up with your heat loss). If you are putting the tubing in a “staple up” or below the sub floor type installation, there may be issues with meeting the heat loss through the sub-floor material with the lower delivery temperatures that the alternative energy systems can reach. Depending on construction type and room load requirements, you may have to choose the proper type of radiant based on the circumstances.

With the heat source, distribution, and controls for these systems, they can get a little complex. Companies like Radiant Complete (www.radiantcomplete.com) are a good resource and can handle all aspects of your renewable project from planning to installation. Whatever you decide, find out all your options and weigh the pro's and con's. If you have questions, consult an expert!

Author Pete Frank is willing to answer questions from readers on this topic. You can visit www.greenhomebuilding.com to submit your question.

10 Comments:

Anonymous Brian Koles said...

This article is one of the best resources for learning the basics of geothermal heating that we've seen on the web! It has prompted me to contact Radiant Complete about working together.

If readers are interested in similar articles that give an overview of green technology and energy efficiency options, the Resources page at www.GreenTechBuyer.org may be of some value.

Keep the great info coming!

7:50 AM  
Anonymous Paul said...

Great article. Its good to see sustainable development gaining momentum. I think if more governments around the world encourage green building we can make it a standard of home building in the developed world.

11:48 AM  
Blogger Naveed said...

Have you heard of any projects recycling basement cool air back through the home. I know my basement stays about 65-70 degrees and if this air can be kept flowing through your vents you might be able to eliminate the heating and cooling all together. I have seen a website called powerzoning.com that uses this principle.
I have written a college paper on geothermal heating and cooling but I was not sold on the use due to the high energy the pump uses and high cost of installation.

With a low energy blower in your basement you could use this system with minor modification to your vents. If you have any information on anyone using this kind of system successfully please let me know.
Thanks

6:53 AM  
Blogger Kelly Hart said...

Yes, I have heard of that, I have also heard of people putting 2' corrugated piping underground and trying to keep the house at temperature that way. Either way you do it, eventually you will heat it up, or cool it down (depending on the season) to a point where it is not useful any more. I have not seen a model yet that can successfully pull that type of system off for a whole season. They all work in the beginning, but once the delta T is gone between the earth and the air being blow they fail.

The principle is the same as living in a cave, thus should be sound with enough surface area and mass. I just haven't seen it work.

I hope this helps.

Pete Frank

5:26 PM  
Blogger Naveed said...

If the piping is outside and underground contained in a waterproof but breathable limecrete container would this make a difference? I'm assuming that there would always be a 65-70 degree temperature air in that container that is being constantly pumped into the home. Any more ideas on this topic?

6:53 PM  
Blogger Kelly Hart said...

It all comes down to "how much heat or cool are you pulling from that area and how fast can it warm/cool itself back up based on the conditions of the ground. Unfortunately I haven't seen enough research on them to know if they are practical or when they fail. But if you could put it in water and then constantly pump the water it would probably work because it would evacuate the temperature that is being expelled. But you would need to find a big aquifer.

Does that help?

Pete Frank
Project Consultant
Radiant Complete Inc.

3:21 PM  
Blogger Naveed said...

It makes a lot of sense to use something like water. I think it's something worth experimenting with. Thanks for the input

4:56 PM  
Anonymous Chris Williams said...

Pete,

Loved the article. Have you noticed customers asking for geothermal or are you having it to sell it?

Chris

2:09 AM  
Anonymous Pete Frank said...

Chris,

My apologies for the tardiness, I was on vacation last week with my family.



Thanks for the complement! We have been pretty fortunate not to need to put a hard press on the Geothermal sales. Now, that being said, when people are asking about a geothermal systems and why they should pay $14,000 more than a conventional system for that technology there is usually a value proposition and ROI that need to be calculated. But our clientele seems to be a bit more educated than the average homeowner and I believe that they may be doing this same process with every part of the project because they are want what is best long term for their home, not what is cheapest to install. But we are clearly not out banging on doors trying to sell them. In a lot of cases we just provide the proper information, structured in a way that is easy to understand, and the clients choose the Geo because it is the right choice long term. Especially in fuel oil and propane markets, they make more sense than in a natural gas market.

If you had any questions I would be happy to answer them for you.

Pete Frank

9:36 AM  
Anonymous solar panels said...

An often overlooked method of heating and cooling in my opinion. There is little glamour in geothermal and radiant heat compared to solar power and wind energy.

The downside is the energy needed to move the radiant heat around the home. With set-ups still being expensive it's a challenging science to make it's way into people's homes.

9:10 AM  

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