How to Seal the Home Envelope

After you've taken the time to find all the leaks in your home you have to get rid of the leaks to make a difference. In most cases this is as simple as sealing the leaks using caulking, weather stripping or spray foam insulation. I typically recommend starting with your ceiling and then working your way down.

To help you with this process, here are some typical leaks sites, based on location, and how to correct them:

Ceiling:

1. Recessed lights: In most newer construction homes, recessed lights will be at least insulation-contact approved, but some may be ICAT- or insulation-contact air tight. This means that they don’t allow air to leak. One of the problems with recessed lights is that they may be ICAT rated, but the wrong trim kit installed. Most of the time, if your light is leaking, you can replace the $5 trim kit with an airtight one, and it makes a huge difference. If this is not the case, you can either replace the light with an ICAT or install a preformed cover that creates an airtight seal around the light. These covers can be ordered typically from the same Websites that sell battic covers.

2. Attic Stairs: Like recessed lights, your attic stairs are a large leak site. To seal these, and insulate, you can install a battic cover. These covers can be bought or built. If your stairs are old and don’t fit tight you may also want to consider replacing the stairs to help get a better seal

3. Bathroom Vents and Lights: The leaks at these typically occur due to a gap between the boxes and the drywall. You can simply caulk or foam the gap. Bathroom vents can leak at the duct. In newer models, this is reduced with a damper that opens and closes with operation. This damper can get stuck or may not seal completely. If you don’t have the damper, you can replace the fan with a newer model, or you can install a damper at the end of the duct where it exits the home.

4. Chimney Chases: Chimney chases often go from the first floor all the way to the attic without being sealed. While it is not advisable to insulate around the chimney due to fire hazards you can seal off the top of the chase using metal and fire caulk.

Interior/Floor:

1. Doors and Windows: Most of the leaks in the walls will occur at either the doors or windows. This can be corrected with weatherstripping and a few other techniques. Due to the various ways to correct, I will address how to correct these leaks in a separate article.

2. Plumbing: These leaks are simple to correct. They will typically occur at gaps between the pipes and drywall. You can correct this by caulking or foaming the gap depending on the size.

3. Electrical Outlets: These only account for 2% for your total leakage, so I typically say not to worry about them at first, but they are an easy to fix. Special gaskets can be installed behind the cover. To get a full seal, you have to use safety covers to seal the outlet holes.

4. Duct boots: Ducts will get their own article, but the boots fall under the envelope. The boots are the metal items that you see coming through the floor or ceiling (yes, these can also fall under the ceiling section). Since the leak is occurring due to the gap between the boot and the floor/ceiling, these leaks are not really in the ducts themselves. To fix this leak, you can either caulk, use foil tape, or mastic the gap.

Unfinished Basement/Crawlspace:

The basement will have a lot of the same leaks as the home, so you can follow a lot of the same steps as above. Also, if the insulation is on the basement ceiling, you may want to treat it more like a crawlspace. My advice is to seal the basement as if you were going to finish it, but time and money may dictate otherwise.

1. Rim Joists: If your rim joists are not insulated, you can seal and insulate them using spray foam. The amount of foam required is more than the standard can foam is capable of handling, but canister kits are available for large jobs. Rim joists in the crawlspace are typically going to have insulation in contact with them, and you can sill penetrations in the floor so sealing these may not be as high a priority in that situation.

2. Foundation Penetrations: These are easy to see and can be corrected by filling the gaps with spray foam. Again, depending on the construction, these may not be as important for air sealing when in the crawlspace. However, they should be sealed to help prevent pests from entering the crawlspace.

3. Floor penetrations: In the crawlspace, these may be a little harder to find (due to the insulation), but all electrical, plumbing, and HVAC penetrations should be sealed using fire caulk or spray foam, depending on the size of the gap. You may have already sealed a few of the gaps from the inside, but it still helps to seal from this side, also. Most of these gaps are going into wall cavities. The air in the cavities can find more than one exit, so stopping the source of the air helps tremendously.

Use a rain barrel.

While this energy tip may not relate to electricity or gas, it relates to another resource that can be overlooked. It can also save you money if you pay for your water! Use rain barrels to collect water from your roof or other collection systems, and use this water to water you plants and yard. Barrels can be purchased or constructed.

Have You Ever Seen a Home With Lungs? (Why Your House Doesn’t Have to Breathe)

Every day, I am presented with the argument that a home can not be sealed tight because it must breathe. A long time ago, a friend and colleague of mine answered this comment by asking,“Have you ever seen a house with lungs?” Of course, the answer to this is no, but many people still believe that their house must get fresh air to breathe.

What you must remember is that it is not the house that needs fresh air, but the occupants of the home. Also, you have to realize that everything we put in a house doesn’t need to be there, so we need to get it out. You may ask, “Isn’t this basically the same thing as the house breathing?” The answer to this is yes and no. Currently, many builders believe that fresh air needs to enter the home, but don't really care how or where. This can be a real energy buster for you if your home gets too leaky! What you want to do is control how much and where the fresh air enters - and let’s not forget about getting rid of the stale air.

You do this by creating a tight home that has few uncontrolled air leaks or air changes. Air changes are the number of times the air in your home is exchanged with fresh air over a given period of time. Typically, this is figured over an hour. Often times, air exchange rates are amplified for measurement purposes. This is done with a blower door that decreases the pressure in a home, and is usually measured at 50 Pascals. Most new homes that I see range between 5 and 8 air changes per hour at 50 Pascals (ACH50). However, there are the exceptions in which they have leakage below and above this range. I like to see homes around 3 ACH50, with controlled ventilation. The most efficient homes that I see are in this range and will typically have ERV’s or other means of air changing. (An ERV is an additional piece of equipment for your HVAC that can exchange and condition air.)

Once the home is tight, you need to get air in and air out. Building codes may state how much air you need to bring in and out of a home, so check there first! They may also limit the amount that can be brought in by natural means, such as leakage or passive ventilation. Once you have checked with someone who knows about the codes, you will want to get someone who is knowledgeable about exchange rates and how to achieve them. This is done by various means, and each has its own pros and cons. You may see the use of any of the following types or a combination of them:

1. Passive ventilation
This is ventilation that operates on natural forces and is most commonly seen in crawlspaces and attics; however, you may see it on exterior of walls as well. This is used to lower temperatures and humidity levels in these areas.

2. Spot ventilation
This is used to remove contaminants/stale air from a central location. An example of this is bathroom exhaust. Spot ventilation is very important to remove unwanted moisture in bathrooms and kitchens, but it can produce a negative pressure on the home. Just make sure you don’t go overboard on the size of the fan.

3. General Ventilation
This is simply the ventilation of the entire living space using fans. It may be broken down into sub categories or considered supply only or dilution ventilation, depending on the source. Dilution ventilation is achieved by only pumping in air to dilute stale air, and it can create a positive pressure on the home. The exhausting of air is not controlled. It can be achieved via a standalone unit or through the HVAC.

4. Exhaust Only Ventilation
Exhaust can be sub category of general ventilation, and it is achieved through exhausting of air only. This may seem like spot ventilation, but it is for the whole house and not just a certain location. It can be achieved through an exhaust fan in a central location, the HVAC unit, or through a bathroom fan that is designated to permanently stay on. This can cause a negative pressure on the home, because the intake of air is not controlled. A negative pressure can cause back drafting.

5. Balanced Ventilation
This is also called supply and exhaust ventilation. The air taken in will typically equal the air exhausted. This is often achieved with piece of equipment, such as an ERV or HRV. It keeps a balanced pressure in the home, and both sides of the air exchange are controlled and possibly conditioned to help lower heating and cooling loads.

There are several systems and variations on the ventilation types mentioned above. If you are building a home or just working to better your current one, talk to your contractor or someone knowledgeable about ventilation to work out a system that best fits your home, needs, and budget.

Install Energy Star Appliances

Since we are taking the time to talk about ventilation this week, I thought I would just mention Energy Star appliances. Many people will probably say that they already know about this, yet wouldn't understand its connection with ventilation. Many people don't realize that there are appliances and fixtures approved by Energy Star other than the typical dishwasher and refrigerators!

In respect to the topic on ventilation, there are Energy Star ventilation fans. When looking at a system that may be using one of these fans to provide ventilation, it is a good idea to have one that will save you energy.

So next time you’re looking for a new appliance or fixture, check to see if there is one that is Energy Star approved, because you just may be surprised by what you find!