Building a new house? Tips for a healthy and energy-efficient home
BY CHRISTINE CROCKER AND DAVID JOHNSTON
Building a new home is a big, complex project. Several critical construction considerations should be followed to ensure your new home is both energy-efficient and healthy for you and your family. Many of the following recommendations can only be done at the point of new construction or are significantly less expensive to do up front rather than after the home is finished. For others, the added upfront cost will save the homeowner in the long run — in reduced energy consumption, reduced maintenance cost, and increased health and productivity. So, it’s important to review these recommendations with your contractor prior to starting construction and ensure they are followed.
Goals for your new home:
Pollutant and pest-free
Tip #1: Site work - Drainage, drainage, drainage
The building and site must provide effective drainage measures to control both surface water and sub-grade water, to prevent it from entering the building. If the site is difficult to drain, build on a slab instead.
Tip #2: Install radon preventive features
Radon is a colorless, odorless gas that comes up through the ground and gets trapped in buildings. It’s the #1 cause of lung cancer in nonsmokers. One-third of Maine homes (half in Cumberland County) have a radon problem. Installing radon preventive features at the point of new construction is not only cheaper, it is more likely to be effective without the need for an electric fan.
Tip #3: Waterproof foundation walls
Waterproofing (not damp-proofing) bridges the cracks that will form in your concrete foundation.
Tip #4: Insulate the ENTIRE foundation - a “koozie” for your basement
Insulate under the slab and all the way up all foundation walls. This is best done at the point of new construction outside the foundation walls, but it can be done from the inside later.
Tip #5: Install a moisture barrier under the slab
A moisture barrier under the slab is critical for managing both water and water vapor. It can also serve as one of your radon-preventive features.
Tip #6: Install a thermal and moisture barrier between the concrete foundation and the house structure
This prevents moisture from wicking up into the structure and causing water damage.
Tip #7: Cellar windows are for light only, not ventilation
It is a common misconception that opening basement windows in the summer provides good ventilation. Actually, it leads to condensation issues, which can then cause mold and mildew.
Tip #8: Dehumidfy
Even well-built, properly drained and fully insulated foundations may have moisture problems in Maine during the summer months. Be prepared to dehumidify your basement with a good quality, professional-grade dehumidifier.
Tip #9: Protect your building materials from the weather
Ensure that materials are well covered during the entire building process, and send back or throw out any moldy materials.
Tip #10: Avoid traditional single-stud walls with fiberglass insulation
This style of framing allows heat to escape through the wood studs. Newer, better options such as double wall framing are available and should be discussed with your contractor.
Tip #11: Caulk, caulk, caulk
Account for high grade caulking in the budget (a case or more to do it right). Air sealing should be part of your housing budget, not an incidental. Sealing all cracks is critical for both indoor air quality and energy efficiency.
Tip #12: Plan for ductwork before you start framing
Allow space to keep the ductwork inside the heated envelope, rather than in attic space.
Tip #13: Pay careful attention to the make-up of the “sandwich” of your walls & roof
It is extremely important that the products you choose and the order in which you layer them work together to keep liquid water and water vapor out and provide a pathway for it to escape if (when) it finds its way in.
Tip #14: Avoid plumbing in exterior walls - not even sewer drainage
Condensation issues and frozen pipes are expensive to repair after the fact.
Tip #15: Flashing, flashing, flashing
Spend whatever is necessary to properly flash all windows, doors, eaves, valleys, decks, chimneys, plumbing stacks, exterior lights and other penetrations or areas that alter the natural drainage plane.
Tip #16: Rain screen/drainage plane
An air gap behind the cladding is an excellent idea. Cladding is for looks, not moisture management. A good storm will bypass the clapboards/siding no matter what they're made of. So, give the water a way to get out.
Tip #17: Manage insulation cost: Doubling the R-value will not halve operational costs
It is more important for the insulation to be continuous (no gaps or holes) than for it to be thick.
Tip #18: Install fully-ducted, balanced ventilation
The purpose of your new home is to provide a space for people, and people need ventilation. Fully ducted, balanced systems deliver fresh air to and exhaust pollutants from all areas of the home; they are also more energy-efficient than passive ventilation or exhaust-only ventilation. Your goal: Build tight, ventilate right!
Tip #19: Use sealed combustion heating appliances or consider heat pump and/or solar strategies
Heat pump technology has come a long way, and is consistently reliable down to -25 ̊F. See the heat pumps article on page 31 to learn more.
Tip #20: Finishing smartly
Use low VOC paint, and prioritize solid wood cabinets and trim over products with lots of glues. Allow new materials to off-gas prior to occupancy. Don’t install carpet in any area likely to get wet. Place foundation plantings at least 24” from the home, and away from any exterior vents. Keep earth sloping away from the home and no closer than 8” from any wood surface.
Construction Resources for Cold Climates
Builder’s Guide to Cold Climates by Joseph Lstiburek
Available from Amazon and other booksellers.
ASTM E1465 Radon Standard for New Construction
PDF copies available for purchase, www.astm.org/Standards/E1465.htm
U.S. EPA’s Indoor Air Plus Program
www.epa.gov (search for “Indoor Air Plus”)
U.S. Department of Energy Builder’s Challenge Guide to 40% Whole-House Energy Savings in the Cold and Very Cold Climates
www.energy.gov (search for “Cold Climate Challenge”)
For more construction resources for healthy, energy-efficient Maine homes, visit www.maineindoorair.org or contact the Maine Indoor Air Quality Council at 207-626-8115.