Friday, February 18, 2005
How NOT to Build a Green Building: Building Shell
I've spent alot of time discussing products and methods of building that results in green buildings. The amazing thing is small changes in normal practices can yield huge results. Many of these normal practices also result in a poorly performing building, even before energy costs are calculated. Many of these small changes do not cost any more money than normal practices, it's just a matter of awareness of the builder and designer.Building Shell
Make the roof black. This will increase the heating load due to solar gain. Flat black tar roofs are the best for this.
[Light grey shingles and white roof "tar" are products that do not cost much more, if anything additional at all.]
Ignore or poorly address the concept of the building envelope. When the building envelope is not continuous, heat and moisture can migrate in. This is especially a problem with vaulted ceilings, crawlspaces, partially-conditioned attics, and garages. Having a hole visible through the roof from a closet is a great example of this.
[This is a design issue. Designers need to be extremely aware of where the line is between conditioned and unconditioned spaces. Insulation and a vapor barrier should be at this line, should be continuous, and should be built as designed.]
Get the cheapest doors and windows possible. You get what you pay for. In this case, there will be more air infiltration and more solar gain through the windows.
[Windows can be pricy, but they are well worth the additional expense. They increase the comfort level of the occupants and reduce heating and cooling costs.]
Use batt insulation and install it without stapling it up correctly. If done poorly, batt insulation will slide down the wall, leaving the wall uninsulated.
[Installing batt insulation correctly takes only a few moments longer per 16" section. People who are proficient at doing this will not even notice the increased time. A better option would be a spray-in insulation, but there is a substantial cost increase for this.]
Design the garage integrated with the building and without adequate air barriers between it and the living space. This design flaw will not only lose energy through the garage, but can cause CO infiltration into the house during the winter. Since buildings are negatively pressurized, they suck air from the outside and from garages.
[Integrated garages need to be outside the building envelope and special care should be taken to ensure this separation. A better idea would be a detached garage or a carport.]
Remove the vapor barrier out of the building job, then increase the indoor humidity to over 30% in the winter. Bad, bad things happen in this scenario. Water vapor flows from higher humidty spaces to lower. This also can happen through walls under the right circumstances. In the winter, the outside relative humidity is very low, around 15-20%. 30% is about the lowest humidity that people need to be comfortable in a space. If water condenses inside the wall, particularly inside insulation, mold will form and the building structure can be severely damaged.
[Include the vapor barrier, do not over-humidify the space and be aware that moisture infiltration WILL happen. The designers need to account for moisture in the walls by providing a drainage plane on the correct side of the vapor barrier: water condenses on the barrier then drains safely out of the building.]