Energy Efficiency Doesn’t Just Happen
Brad Cook, the proprietor of Building Performance Services, was the guest of the MRV Chamber’s latest Coffee and Conversation series. With the building and renovation season nearly upon us he came to talk about energy efficiency for small businesses and home owners.The conversation was so “content rich” we decided it would be good to outline some of the material along with links to go along with the video of the presentation.
As a BPI Certified inspector and energy efficiency expert he imparted a tremendous amount of information and strategies. He espouses thinking of your home holistically and for developing an plan for your home or any building for that matter.
Brad suggests that before you do anything you need to assess the situation and follow…
Brad’s Rules for Assessments and Construction
- “Always look at the whole picture” (including possible future changes)
- “The more you look, the more you see”
- 1st Corollary- “If you don’t look, you don’t see”
- “You can never take enough pictures”
- “If you don’t test, you guess”
- “You can never ask enough questions”
- “When you change one thing, you usually affect something else”
- 1stcorollary- when you clean something, something else has to get dirty”
- 30 Year Rule- “You only make major renovations or repairs to your home about every 30 years, so do so accordingly” (use materials and standards that will last that long and prepare for future innovations; see rule #1)
Then after careful assessment you are ready to develop a plan for your home that prioritizes renovations and upgrades.
There are a lot of factors to consider and Brad exploded a few myths and misconceptions about energy efficiency.
ENERGY MYTHS & MISINFORMATION
MYTH #1 – I am building a new house, and I don’t want to make it too “tight” because a house has to breathe.
As we try to make our homes more comfortable and energy efficient, we are making them tighter, adding a variety of insulations, air and vapor barriers and using new materials and technologies. If we don’t pay attention to what, how and where equipment and materials are installed, we may be creating other problems and we won’t get the results expected. As we make our buildings tighter, we must pay closer attention to our Indoor Air Quality ( IAQ), which includes moisture (RH), CO, CO2, VOCs, mold, etc.
Our mantra is “build it tight and ventilate right”. We want to control the ventilation of our buildings and not let Mother Nature do it for us, because she will ventilate when we don’t want it (when it is below 0°F outside) and not ventilate when we need it (the house is filled with cooking odors).
You do not know how tight your building is unless you test. I have tested houses from the early 1900s that have not been remodeled or weatherized but are tighter than the average house built in the early 2000s. I have tested new houses that were draftier than the average home built 20-30 years. (see Rule #4).
The average house today exchanges all of its interior air with fresh air about once an hour, whereas a new home built to current energy standards will exchange about ¼ of its air every hour.
When air is heated up, it expands and takes up a larger volume, but it has the same number of molecules, including the same number of water molecules. Therefore, when we heat up air the RH (Relative Humidity) goesdown.When air cools down, the opposite happens and the RH goes up.Thus, when it is cold outside and your warm air in the building leaks out (it is less dense than the cold air outside) it draws in the cold outside air. When that outside air is at 10°F and 100%RH and it is drawn inside and heated to about 70°F, the RH goes downto 10%.
The houses of the 18thand 19thcentury were so drafty that the entire volume of air in the house was typically exchanged about 3-4 times an hour. Since any moisture generated by typical tasks, such as cooking, bathing and breathing left the building along with the warm air, people had to put a pot of water on the woodstove to try to get that RH up away from the single digits.
A general indicator of how tight a building might be, assuming that there are no unusual sources of humidity (such as lots of plants or lots of pets or even running a humidifier), or NO reasonable sources of humidity, is whether there is condensation on the windows. For insulated glass windows, or single pane windows with a storm, if there is NO condensation when it is in the single digits outside, the house is drafty. If there is condensation when it is in the upper teens or higher, the house is tight with poor ventilation.
MYTH #2 – Replacing drafty windows will save lots of energy
Glazing makes up about 15% of the total wall area of typical building. Replacing one window will cost somewhere around $700-1,000. The R-value (insulating value) of a typical window described above, the R-value will go from about an R-2 to 2.5 (R-2 cuts the rate of heat loss by conduction in half) to an R-3 to 4 (cutting the rate to about 1/3 or 1/4th). The economic payback will be somewhere around 20-30 years, or more. If a window is “drafty” it is likely coming from the rough opening (the gap between the window itself and the wall framing). That can be corrected by pulling the trim and the (typical) fiberglass insulation and sealing the gap with a one-part foam to air seal.
MYTH: #3 – “My house is new, it must be energy efficient”
Although Vermont has had an energy code since 1998, it is not often followed., although more and more municipalities are requiring a completed RBES certificate, Certification of meeting the standards (currently VTRBES-2015 or VTCBES-2015) is solely the responsibility of the General Contractor. In many of the cases where an RBES or CBES certificate was filed, the letter of the standards may have been met, but not the intent, resulting in problems down the road.
MYTH #4 – “Expensive electric space heaters must be very energy efficient”
The 2ndLaw of Thermodynamics: “energy can neither be created nor destroyed, only transformed from one form to another). Electricity has 3,413 BTUs per Kilowatt-hour. NO electric heater designed to be plugged into a typical outlet will draw more than 1,500 watts. Turned on for 1 hour, such a heater will provide the same amount of BTUs as any other electric heater (1.5KwH x 3413 = 5,120 BTUs in that hour). The only difference is how that heat is distributed to the area (convection and/or radiation).
MYTH: #5 – “My boiler (water heater) is new, so it must be efficient”, “A wall-hung,, condensing boiler is the most efficient” or “A tankless water heater is the most efficient”
If the combustion appliance (this goes for heaters as well) has a standing pilot light”it is not efficient (around 80-82% efficiency) AND burns about 2-3 gallons of propane a monthjust for the pilot! (turn off the pilot if not using the appliance for a long period)
If the boiler is a condensing boiler and it will not see return water cool enough to condense water vapor, (<~140°F) it will not be 96% efficient, but more like 90% efficient.
A tankless water heater will not be efficient if it experiences a lot of short draws of hot water, which is often the case with only one or two people. They shine when there is often a need for a lot of hot water, such as in a second home where a lot of people come up for the weekend, an inn or B&B or a business that uses a lot of hot water.
For the occasional need for some hot water, a heat pump water heater is the best choice.
Myth #6 – Heat tape will solve ice damming issues
Think before installing heat tape or standing seam roofing to “solve” ice damming. Most ice damming is cause by warm air leaking out of the house into the roof framing, so air sealing is the best fix. Once you put metal roofing on, you have burned your bridge for getting into the roof framing to fix air leaks.
Next would be little insulation in the roof. A rafter bay can only hold so much insulation. If the rafters are only 6” deep, that would be about an R-19 for fiberglass batts. IF you were to strip off the roofing or inside ceiling and fill the rafter bays with a closed cell SPF (spray polyurethane foam), you would achieve about an R-35 (and it is expensive).
The better solution is to add a few layers of rigid insulation on top of the roof. The current energy code calls for a minimum of R-49 for a roof.
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