The Energy Specialist must assess the basement area for possible energy efficiency improvements. If an element is eligible for enhancement, the Energy Specialist will gauge the area of each element and determine the complexity of framing cavities. Refer to Section 2.9 for more information about calculating areas.
The Energy Specialist must determine how the customer uses the basement. He should also determine its link with the building envelope to assess the potential for energy improvements. This guides how the basement measures will be suggested. Usually, basements are semi- conditioned and considered inside the thermal envelope because of the existence of mechanical equipment (heating and DHW equipment) and heating distribution systems.
Trials to decrease heat loss by separating the basement from the home are most of the time unsuccessful. Exceptions might include some crawlspaces or basements with big openings to the outside. In the rare cases where the basement is out of the thermal envelope’s territory, eligible measures to commend include:
For basements that are plainly outside the thermal envelope (like a vented crawlspace):
Heating System Distribution Improvements:
- Duct Sealing – Recommend that all ducts located outside the thermal envelope be sealed with mastic or mastic tape to form a durable, tight seal. Duct sealing shall be recommended in conjunction with duct insulation. An HVAC Mass Save contractor should recommend these improvements for implementation.
- Duct Insulation – Recommend fiberglass duct insulation with a foil vapor retarder on all heating ducts located outside of the thermal envelope. Duct insulation shall be recommended in conjunction with duct sealing. An HVAC Mass Save contractor should recommend these improvements for implementation.
- Hydronic and Steam Pipe Insulation – Recommend pipe insulation for all heating pipes located outside the thermal envelope.
Basement / Crawlspace Ceiling Insulation:
If the basement is located outside of the thermal envelope, ceiling insulation can be used to complete the thermal envelope.
- Fiberglass Insulation – If the ceiling joists are spaced appropriately, fiberglass insulation shall be recommended. Installation of thermal barrier board insulation in addition to the fiberglass may also be recommended.
- Dense pack cellulose – If minimal to no pipes or wiring are present, the basement is very dry, and the joists are unevenly spaced, recommend ceiling dense-pack cellulose. If the space is already enclosed, recommend dense-pack cellulose. If the space were not enclosed, reinforced mesh or thermal barrier board insulation would need to be specified to hold the cellulose in place. Pay close attention to how difficult it may be to install cellulose in the space and if it is possible.
- Cellulose – If the unenclosed area can be adequately air sealed before insulating then dense-pack cellulose is not required. Specify reinforced mesh or thermal barrier board insulation and cellulose along with air sealing.
- Thermal Barrier Board: To be used to encapsulate insulation from the exterior air temperature and humidity. Should be recommended when minimal potential roadblocks such as pipes or wiring exist that can make it difficult to achieve the program-required thermal boundary.
Basement Stairwell Insulation:
Insulating the stairwell and door is suggested as required to complete the thermal envelope if the basement is outside the scope of the thermal envelope and basement ceiling insulation is endorsed.
- Fiberglass Insulation – If the joists are open and regularly spaced, recommend fiberglass insulation.
- Cellulose – If the joists are open and irregularly spaced, recommend reinforced mesh or rigid board insulation and cellulose.
- Dense pack Cellulose – If the stairwell is enclosed, recommend dense-pack cellulose.
- Stairwell Door – Insulate the stairwell door’s back with rigid board insulation in conjunction with the basement stairwell insulation.
Basement Rim Joist Insulation: (materials are based on program administrator)
- Fiberglass Insulation – When joists are appropriately spaced, recommend fiberglass insulation for the rim joist area in basements that are in the thermal envelope. Recommend air sealing of the rim joist with fiberglass batt insulation to ensure an aligned air barrier and thermal boundary.
- Spray Foam Insulation – Consult with PA for materials used.
- Thermal Barrier Board – Recommend it only in special circumstances. Consult with PA for the right situations.
- Insulate Basement Exterior Door –Rigid board insulation for the back of uninsulated exterior basement doors that are in good condition should be recommended, along the thermal boundary.
NOTE: Basement locations requiring LV approval for Thermal Barrier Board:
- Above Grade framed walls
- Foundation Walls
- Walkouts
- Any space used as living space
Above Grade, Open Framed Basement Walls:
- These might be insulated using batt material only if the wall cavity is unfilled and the area has a specific heating supply register/baseboard.
- Always tell the customer that batt insulation would be installed without a vapor barrier.
Dirt Floors:
All reachable dirt floors shall be suggested for coverage with 6+ mil polyethylene plastic sheeting. If a dirt floor area is inaccessible and inadequately vented, then adequate ventilation should be added or the crawlspace is made accessible unless the exposed dirt floor consists of less than 10% of the total footprint of the building.
Exception: No Vapor Barrier is desired if installing Thermal Barrier Board on a crawl space ceiling has no link to the basement area.