The best time to make major energy retrofits (also called deep energy retrofits) is during a renovation. This is when you’re making major changes to the building, and probably getting a building permit. Ideally, the house will be vacant during this process. Here are 10 major energy retrofits that should be part of every home renovation job.
10 Major Energy Retrofits
- Attic air-sealing
- Wall air-sealing
- Attic insulation
- Wall insulation
- Floor and foundation insulation
- Windows and Doors
- Shading and reflective roofs
- HVAC system
- Duct improvements
- Bonus: Non-Energy Benefits
We put air sealing first because it’s very important if not the most important part of major energy retrofits. You also need to seal air leaks before they are covered up by insulation and finished surfaces. The attic floor can be one of the leakiest parts of the building, and also the most difficult to seal. If you remove existing attic insulation then you’ll have full access to all of the seams and junctions in the attic floor. And that means you can air-seal them. Walls typically leak at the top and bottom of the wall cavities, and at the seams where the exterior sheathing panels meet. The leaks may be small, but there can be a lot of them and that adds up to a lot of air leakage.
Once you’ve air-sealed the attic, and fixed any other issues (like wiring and plumbing) you can install new attic insulation. Install as much as the attic can handle. Attic insulation is relatively cheap for the benefit that it provides. Install insulation baffles at the eaves so the insulation doesn’t block the attic vents.If you have little or no wall insulation, you can demolish the interior wall sheeting and install an inexpensive fiberglass batt. Or take advantage of the opportunity and install dense-pack fiberglass. Be sure to get your air sealing work done first. The floor and foundation are often overlooked when it comes to insulation. But it’s an important part of the building’s thermal envelope. *** expand on this ***
If you have little or no wall insulation, you can demolish the interior wall sheeting (drywall) and install an inexpensive fiberglass batt. Or take advantage of the opportunity and install dense-pack fiberglass. Be sure to get your air sealing work done first.
The floor and foundation are often overlooked when it comes to insulation. But it’s an important part of the building’s thermal envelope. The ground underneath a building tends to stay at a constant temperature. However, that temperature is generally lower than the desirable indoor temperature. So if the floor and foundation are left uninsulated there will be heat loss through the floor.
Big Ticket Items
The savings gained from replacing windows and doors don’t usually have a good payback. This is because windows and doors can be so expensive to purchase and install. But if you’re replacing them as part of the renovation, then buy the best windows and doors that you can afford. Look for low U-factors. U-factor is a measure of how much heat transfers through the window or door assembly. Lower U-factor means lower heat transfer. If you live in a hot or sunny climate, pay attention to the SHGC (Solar Heat Gain Coefficient). It’s also very important to make sure you install flashing correctly to prevent water intrusion, and air-seal to prevent air leakage.
Homeowners in Northern climates should never pass up the opportunity to install exterior foam insulation or other exterior insulation when replacing siding and windows. Replacing siding and windows is a common combination of home improvement.
Exterior shading and reflective roof systems can really help reduce solar heat gain, which will reduce your air conditioning costs.
If your HVAC system is very old or inefficient, consider replacing it. Newer systems can be much more efficient than older units that waste a lot of energy. The newer systems can also provide more comfort for the building’s occupants. Also, consider the size of the new system. Now that you’ve made all of the improvements above, you may be able to install a smaller system. This will save you money on the equipment and also on your power bills. If you improve the HVAC system you’ll likely need to improve the duct system to match.
The role of ventilation is to provide clean and healthy indoor air for the building’s occupants. We call this Indoor Air Quality or IAQ. We can use ventilation for IAQ in many different ways. A basic ventilation system can be a simple as exhaust fans that pull air out of polluting areas like the bathrooms and kitchen. The replacement air generally comes into the house through air leakage in the building envelope. This isn’t the best ventilation option.
A better option is a whole building ventilation system, like a Heat Recovery Ventilator (HRV) or an Energy Recovery Ventilator (ERV). These completely closed and balanced systems exhaust polluted air to the outdoors and bring in a balanced quantity of fresh air. In the process, they transfer heat between the incoming and outgoing air streams. This helps to conserve energy.
Balanced ventilation systems can use the duct from the central HVAC system. But it’s better if they have their own dedicated ducts. If the building is going through a major renovation there’s an opportunity to install a dedicated ventilation duct system. You might also need to do a little demolition to install a ventilation system correctly. Air-sealing a home to 2 air changes per hour at 50 pascals (ACH50) or 0.10 natural air changes per hour (ACHn) can be very difficult without removing attic insulation or moving everything out of the basement.
Important Non-Energy Retrofits
Since you’re getting a building permit you’ll also be going through some building inspections. The building inspector will likely need to check some non-energy components in the building. If there are issues you may need to fix those. But since the building is under renovation, these systems should be accessible.
Smoke and carbon monoxide alarms: If the home doesn’t currently have smoke and carbon-monoxide alarms, those need to be hard wired. Since you’ve removed the attic insulation, it may be cheaper and easier for the electrician to work.
Radon mitigation systems: Radon can be an issue for homes in any part of the country. A radon mitigation system pulls radon gas from beneath the foundation before it enters the building. It’s fairly difficult and invasive to install into a finished building. But it’s easy during new construction or renovation. Proper radon testing can take a month or so to complete. So get the testing done before renovation to see if radon is present. If radon is present your newly renovated and air-tight building could see increased indoor radon levels compared to pre-renovation.
The Take Away
These 10 major energy retrofits should be part of any major home renovation. It would be great if the building codes demanded more energy efficiency performance as part of a major renovation. But even the current inadequate levels of building performance typically aren’t reached for new construction because of a lack of code enforcement. This begs for more continuing education for building inspectors and code officials.