Sunday, February 22, 2009

Geothermal heat pump system

Although the house is using the sun to heat itself, there is a need for additional heating during the cold winter months when the sun isn't shining. For that purpose we installed a geothermal heat pump system to deliver the needed heat with the utmost efficiency. Yes, the system was costly but given how efficient it is, and the desire to have the home completely run by electricity, it was the most sensible option. The house is designed to be convertible to zero energy, once the total energy loads have been determined. ( PV array) The heat pump reduces the amount of electrical energy needed to heat the home.
How does a heat pump work? That is a sum what complicated answer, but the gist of it, is that it moves heat out of the ground and transfers it into you house by using a refrigerant, compressor and an expansion valve the system extracts heat out of the ground exchange while in the low pressure cold side of the system. Not the simplest thing to understand, how you can move heat efficiently even at temps as low as 32F, but it really works and works well. The other component of the system is the radiant floor slab, which allows for low temp water for heating. Once you have reduced you need for heat through super insulating and air sealing the systems cost is dramatically reduced. For this house we purchased the smallest heat pump that we could find, that would not only provide heat but also provide cooling.
Here is where we stuck our necks out. Not many people try and cool their homes through a radiant floor and there are several obstacles to doing this. First of all most houses require more cooling because the are not super insulated, radiant cooling has a limited amount of Btu's it can deliver. Another major obstacle is humidity and condensation which can accumulate on the floor, if you have rug, wood or vinyl this could be catastrophic. We have installed a whole house dehumidification system that can reduce the humidity in the air and also reduce the demand for cooling. You feel cooler when the humidity level is lower ( it's not the heat it's the humidity) reducing the need for cooling. But when there is a demand the humidity level can reduce the dew point and reduce the chance for condensation. Another part is the ceiling fans which may reduce the need for cooling or at least help to move the cool air off of the floor and circulate it around the room. If we do get condensation on the floor, it is not a major problem. The finished floors are stained concrete, so they won't be ruined if it happens and they won't hide the problem under the rug, making it easy to identify and rectify. Here is a video showing the heating and cooling system.



The closed loop, horizontal ground exchange system was shown on a previous video and gives you an idea how the ground exchange is installed.

This is one feature of the house that has been gaining in popularity in the last few years. It makes your energy cost less susceptible to the fluctuations of the fossil fuel market. Electricity cost do not rise 100% in a few months like the oil prices did over the last year, and enables this house the ability to produce all of the energy it needs to maintain itself. To make the final leap to zero energy is a costly one and given the inefficiency and cost of PV panels at this time it is not the most cost effective approach. However I do believe that PV will get better and the cost will come down, to that end an electrical chase was run from the attic space into the utility room for future use. The roof line was designed to maximize the solar gains and make use of all potential solar energy that is available on this site. Hopefully one day soon, the PV manufacturers will make a panel that is at least 30% efficient and costs less than the house itself. At this time the cost to install PV panels that would produce all of the homes energy needs would be between $40-50,000 and would take the full life expectancy of the panels to pay for itself. Not there yet!!!

Tom Pittsley
ecobuilder@aol.com
www.eebt.org

Sunday, February 8, 2009

Green Building, from the ground up

While most of my blogs have been focused on passive solar energy,there is a whole lot more to building an energy efficient or "Green Building". I don't like to call myself a green builder, it sounds kind of trendy and that has never been my thing, but I have been following most of the basic principles for years. Lots of the things that are thought to be green also save money during construction, things like reducing material waste. My current project, has had half of the normal waste of a typically built home, great for the environment but also great for my wallet, I saved almost $1,000 in disposal fees for the project. I have at the homeowners request decide to attempt, to compile all of the green elements designed into this house. My latest video covers some of the features.


I want to take a minute to mention and thank Linda Johnson, (homeowner) without her this project would not have been possible. When Linda first came to me in June of 2008 and told me she had found a lot and wanted to build an energy efficient house, I was ecstatic. Here was my chance to prove that with good design, you could build a very energy efficient, passive solar home at a reasonable cost, and so the design process began. Working together we came up with a house that meets all of her needs while reducing energy needs and costs while using as much solar energy as is reasonably possible.
When I design a building I use a whole house method to make decisions, taking into account the added value and costs. It's kind of hard to explain, but many of the choices we make in the design phase will have an impact on not only the energy usage of the house, but also the costs as well. I have a unique advantage over most Architects, in that I don't just design the building but I also build it. I know how much in cost to build things and how the cost of materials and labor can be reduced through good design. Here are a few questions I ask myself when making decisions about design or materials, first: Does this save energy? Saving energy always saves money the next question is how much energy does it save? How much more does it cost, if it cost more? Is it better for the environment? Will it last longer? Is it produced or available locally? So, here is the list and some information about the advantages and disadvantages of each, most have overlapping advantages that work together to save energy and costs. I know I don't have enough time to cover all of it in this post, but I will continue it into others, when time allows.


Insulated slab on grade foundation

The insulated slab on grade foundation allows us to use the foundation as the heating distribution system for the house. It also has thermal mass properties that allow it to store thermal energy, and regulate the temperature fluctuations of the house. The floor controls the temperature in the house, if the floor is cold the house will be cold, if it is warm the house will be warm. By using radiant tubing embedded in the floor we can deliver heat to the house at a much lower temperature than with traditional heating systems, even better that most radiant systems, that are installed below the floor. The least expensive way to install radiant tubing. The slab only requires the heating system to provide 90F water for heating, under wooden floor radiant requires at least 130F water and forced hot water system require around 160-180F. The lower temperature needed for heating also increases the efficiency of the geothermal heat pump, another whole feature of the house that I will explain in another post. We are also using the foundation as the finish floor for most of the house. When the foundation was poured, we had the concrete guys finish the concrete slab just like you would a concrete floor, polished to a smooth surface. We then covered the floor during construction to protect it from the likes of the plasterers that would make the clean up a nightmare. The finish will be an acid stain with a sealer that will appear much like tile. We cut grout lines into the concrete making it look like a 18"x18" tile pattern, then the acid stain will be applied, neutralized, sealed and then waxed. Once completed it will appear as tiles, but no materials were shipped from afar and did I mention that the concrete used contained 20% fly ash, a waste product from local coal burning plants? No VOC's in the finishing product's.
The cost to do this is comparable to conventional flooring but most of the cost is in labor, making it better for me, not so good for the flooring suppliers, oh yea no waste from left over flooring materials.
So this is just one feature of the house that contributes to the green design, I will list more later things like how we reduce electrical and water demands through appliances and even some strategies to reduce vampire loads. How natural light is used to reduce need for lighting and how ventilation can be used to improve indoor air quality and energy use. How more insulation and reduced air infiltration can reduce the need for heat and add to comfort. How passive and active solar energy is incorporated into the design, that has the potential to make this a true zero-energy home. For me these things seem simple but trying to explain how all of the individual decisions made while designing a house, and all of the choices made regarding materials contribute to the energy and cost of building, is much harder to explain in writing. Here is a quick list of other features of the house.

Whole house design
Oriented for solar
Structural Insulated Panels
Heat recovery ventilation
geothermal heat pump
thermal mass windows
energy efficient appliances
HP adaptable
passive solar
active solar
recycled materials
durable materials lasting longer than 30yrs
low maintenance
water reducing elements
electrical reducing strategies
PV ready with electrical conduits run

I am sure I have skipped over some but I will continue this at a later date with more explanation of all of these features and pictures as well. Stay tuned.

Tom