There are many differences between manufactured (mobile) homes built before the HUD Code took effect in 1976 and those built afterward. Many manufactured homes made before 1976 are likely to have the following:
- Air leakage through walls
- Little or no insulation
- No vapor retarder in the roof cavity
- Uninsulated heating system ducts
- Uninsulated doors.
If you have a pre-1976 manufactured (mobile) home, you may want to make the following energy efficiency improvements to reduce heat loss:
- Install energy-efficient windows and doors
- Add insulation to the belly
- Make general repairs (caulking, ducts, etc.)
- Add insulation to your walls
- Install insulated skirting
- Install a belly wrap
- Add insulation to your roof or install a roof cap.
Instead of rolling back the roof, many installers prefer to use roof caps for insulating, in spite of their inferior performance. Roof caps come in kit form and consist of insulation boards, usually of dense fiberglass, with a synthetic rubber or metal covering. Roof caps can insulate the roof to R-19 without disturbing the existing roof. If all leaks in the old roof covering are sealed, the old roof acts as a vapor retarder, eliminating moisture problems and the need for ventilation.
Also, blowing loose-fill insulation into an existing manufactured home is difficult because of the narrowness of the wall and roof cavities. Pre-1976 homes often had only 2" × 2" studs (5.08 cm × 5.08 cm) (new manufactured houses are required to have at least 2" × 4" [5.08 cm × 10.16 cm]). Trusses also hinder adding more roof insulation. Rolling back the roof to add insulation can lead to realignment problems and leaks. Furthermore, if the rollback method is used, adding some type of mechanical ventilation system to alleviate moisture condensation problems in the roof cavity may be necessary.
The above energy efficiency measures are based on experiments conducted on pre-1976 manufactured homes by the National Renewable Energy Laboratory (NREL) from 1988–1991. A survey of 36 mobile homes by the Colorado Division of Housing found that using these NREL-developed retrofit measures resulted in a 31% reduction in heating fuel usage.
To improve your home's energy efficiency, you should also consider the following:
Caulking and weather stripping windows and doors, especially if you can't replace them with more energy-efficient ones
Air sealing any openings around plumbing fixtures and ducts
Using energy-efficient lighting and appliances.
Energy Savers: Manufactured Home Energy-Efficient Retrofit Measures