Tuesday, December 30, 2008

Reduce Moisture Risk with Properly Installed Vapor Barriers/Seal to Prevent Heat Loss

A successful energy plan begins with taking the right steps to eliminate heat loss and avoid moisture problems. Every crack that allows heat to escape, as well as the vapor barrier that prevents moisture problems, affects the energy efficiency of your building.

Make sure you have sealed every gap around doors and windows. Also, check for gaps where flues and wiring exit the house. Caulking works well for smaller holes, while spray foam like Great Stuff is good for larger gaps.

Attach vapor barriers, at least 6 Mil thick, to the warm side of walls. This prevents moisture from entering and causing damage to walls. Overlap the pieces of plastic with a generous amount, and tape the seams. Tape punctures to avoid moisture issues. Remember to tape the plastic to electrical outlets, heat vents, and light fixtures. If room permits in the space above your ceiling, seal any penetrations from the top. Drywall screws may puncture a hole in the vapor barrier and require sealing. Where the vapor barrier runs into existing framing there may also be gaps to seal.

Air is able to travel through small penetrations in framing for long distances. This results in moisture related problems. Seal any penetrations, such as those for wiring, to stop air movement. Other penetrations may be due to construction methods, plumbing, and heating.

Once you have sealed cracks/gaps/penetrations and the vapor barrier is in place, it’s time to insulate.

Thursday, December 18, 2008

Geothermal (Ground-Source) Heat Pumps

Geothermal Heat Pumps (GHPs)

Geothermal Heat Pumps (GHPs), also called Ground Source Heat Pumps, are one of the most efficient sources of heat. GHPs achieve efficiencies of 300 to 600% by taking advantage of the steady temperature of the ground beneath. During the winter, heat pumps take advantage of the warmer ground temperatures to produce heat. During the summer, GHPs take advantage of the cooler ground temperatures to cool your building. The greatest obstacle to the widespread use of geothermal/ground source heat is its cost of installation.

High Installation Costs

Commercial/Apartment buildings have to pay $22.75 a square foot for GHPs. The owner of a 17,000 square foot building would have to pay $386,750 for this system. He would also pay an additional 6-8% design cost to have the mechanical drawings done. In this case, that would be another $23,205 to $30,940.

Residential homes can expect to pay about $20,000 or about $10 square/foot for a 2,000 square/foot home.

Northern Climates – Additional Installation Costs

In northern climates, owners must have backup fossil fuel furnaces. Backups are needed, because once the ground freezes, there is no way to repair the system until spring. These fossil fuel furnaces mean flues, more ductwork, and dampers. Commercial/Apartment buildings might also require alarm systems and fire barriers. In new projects, it is also going to contribute to your architectural/design and contracting costs.

Payback Period

Even with these prices, the payback was five to eight years when fuel oil prices were $4.00 a gallon.

GHPs Act as Air Conditioners Too

Geothermal Heat Pumps (GHPs), like Air Source Heat Pumps (ASHPs), also make good air conditioning systems.

An Alternative that’s even better than Geothermal – Solar Hydronics

Solar Hydronics uses solar thermal panels to heat water before passing it to a storage/holding area. An electric boiler pulls this hot water into the under floor heating grid (Pex-Tubing) directly when it is the desired temperature. If the water temperature is too low, the electric boiler heats it to the desired temperature before passing it into the grid. The cooler water, then, passes back to the solar panel for heating.

The Ideal Situation

Ideally, you would store enough hot water to bypass the electric boiler controlling the under floor heating system. Air Source Heat Pumps (ASHPs) would utilize the latent heat to heat the rest of your home, and you would have generated heat for virtually free – except for a small electric bill you’d have for running the condensors for the ASHP.

Wednesday, December 17, 2008

Air Source Heat Pumps (ASHP's) Answer to Heating Bills

Air Source Heat Pumps (ASHP's) Work Incredibly Well in Cold Climates

Air Source Heat Pumps used to be of limited use in colder regions because their condensors had to be placed outside. Now, we are in a new era of high-efficiency, year-round ASHP's. Condensors can now go inside, allowing them to operate at peak efficiencies year round. HVAC experts can place the condensor in your basement or unused part of your home. The heat that is extracted may be offset by an electric baseboard heater. Even when condensors must be placed outside, they are able to extract heat even at temperatures below freezing. Individuals have reported hearing the ASHP kick in at -10 below temperatures. Of course, they operate at peak efficiencies when the inside and outside temperatures are closer to one another.

Inside Condensors Eliminate Need for Backup Furnaces

When condensors can be placed inside, there is no need for backup fuel furnaces. These backups kick in to supplement or produce heat when the ASHP cannot provide what you need. Condensors that go inside eliminate the need for backup fuel furnaces -- and obviously the need for fossil fuels. Your one utility expense after installation is electricity, and these units draw less amperage than the normal furnace does.

ASHP's also eliminate the need for flues, most ductwork, and dampers. This will save you space, while eliminating a lot of building code issues (fire barriers and alarms). You are simply transporting hot air from the condensor to your living areas.

How ASHPs Work

Refrigerants are evaporating and condensing fluids used by heat pumps to produce heat. A compressor is used to pressurize and circulate refrigerants, in its gaseous state, through the system. This compressor has a condensor (heat exchanger) on its discharge side that condenses the resulting hot and pressurized gas into a high pressure, moderate temperature liquid. This condensed refrigerant is then passed through a pressure-lowering device (expansion valve, capillary tube, etc.) to produce a low pressure, almost liquid refrigerant. It is moved to another heat exchanger (evaporator) where the refrigerant evaporates into a gas via heat absorption. The refrigerant is then returned to the compressor and the cycle repeats.

The heat pump is basically a vapor-compression refrigeration device that includes a reversing valve and heat exchangers so that the direction of heat may may be reversed. This means you may also use these ASHP's as air conditioners.


Engineers at Foehringer Engineering Inc has stated the efficiency of ASHPs are as high as 160%. High efficiency fossil fuel furnaces, at their best, operate around 98%.