How to install windows in a new house

The proper way to install a window;

If you standing near a window in your home and you can feel a breeze blowing across your cheek and the window isn’t open, well it might be because the window was never installed properly. Here is the way that Village Builder’s installs a window so that you never feel a draft.

Just to be clear there are as many different kinds of windows as there is houses in Canada. There are different companies, different shapes, styles and different ways of making windows. I will try to explain the way to install windows in a new home using the most common windows.

Installing a window in a new home;

First you need to frame the opening correctly. This might sound like an easy thing, but a lot of window manufacturers will tell you to frame the opening leaving a ¼ all the way around or less. Keeping the window opening tight might sound like the right thing to do, but actually it is the worst. You need to leave ½ an inch all the way around the window at a minimum!  That means if the window is 40 inches by 30 inches then your framing size should be 41 inches by 31 inches.

Once you have it framed and sheeted then you need to install your house wrap. Pull the house wrap in and around the framed opening stapling it as you go. This helps keep the house wrap tight on the sheeting and also will help keep the air penetration down around the window.

Then you install a strip of waterproofing that is about 9 inches wide on the bottom of the window framing. It should go from one side of the window opening to the other and run up the side of the opening about 12 inches. This will ensure that if and when the window fails the framing will not be rotten when you replace the window.

You then install the window. Depending on the type of window you are installing this could mean a bunch different installations.

·         If installing a window with nailing fins on the outside, you level the window horizontally and move it in or out so that the outside of the window is where you want it to sit. You adjust the window level with shim shingles, placing them 8 inches from the top and bottom on all sides of the window. Depending on how big the window is you might require more shim points. Then you use roofing nails to nail the nailing fins on the outside of the window.

·         If installing a window without nailing fins, then you do everything the same except that you either screw or use finishing nails at the points where you installed the shims to hold the window in place. Remember to countersink them so that they can be filled when finishing later.

Now that the window is where you want it, you then use low expansion spray foam and fill the void between the window and the framing. You must not fill the whole cavity right away, spray in the foam around the whole window moving constantly never stopping in any one place and let it dry. Once it has dried then you may proceed to fill more of the cavity around the window, you will have to do this several times before the cavity is completely full. The dangers of putting too much spray foam around the windows all at once are pretty serious! You can actually break the window if the foam expands too much. Or if the window is an operator you can jamb the window so tight that it will never open.

Some key things to understanding the insulation around the window;

·         Only use spray foam around the window, do not use fibreglass insulation, or roxall. The reason is that fibreglass insulation and roxall are designed to allow air to pass through them; they just slow it down to allow the furnace in the house to warm it up. Spray foam allows no air penetration.

·         Only use low expansion spray foam. I am repeating myself for a good reason. The high expansion spray foam will break the window you are foaming; also low expansion spray foam is denser and is able to restrict the flow of air easier.

·         Make sure the window is in properly because once you spray foam the window it will never move. Spray foam holds so well that you could take out all the screws and nails that are holding the window in place and the window wouldn’t move. Trying to remove the spray foam to move the window later will be a nightmare.

·         Make sure the window is set at the proper depth on the outside of the building not the inside. It’s more important to get the window in the proper place relative to whatever you are placing on the outside of the house. It doesn’t matter if the inside build out doesn’t end up where you want it, if it’s too short then you add a jamb extension on later.

Now that the window is installed and properly secured in its final resting place you can move on to the outside of the window. If your window has nailing flanges then you simple take you’re waterproofing and start by covering the nailing flange to the edge of the window. The 6”to 9” waterproofing will then extend out and cover said distance creating a water and air barrier. You put the bottom piece of waterproofing on first covering the piece of waterproofing that you have already installed and then the sides. The last piece is always installed above the window. This will give you a perfect water and air tight seal around the window.

If your window doesn’t have a nailing flange, then you install a drip cap first on top of the window, and then put your waterproofing over it. This will help direct the water away from the window. Unfortunately you cannot install waterproofing on the sides and bottom of this window because there is nothing for the waterproofing to attach to at the window. So installing the waterproofing becomes a waste of time and money.

All windows should have a drip cap installed over them regardless of where they are installed in the house.

When you complete the siding or stone around the building, you’re going to want to go around and caulk all the windows and the trims that are touching or placed near them, especially any trims above the window. Use a good quality outdoor weather resistance caulking. Caulk all joints that you can. This will help stop all air leakage around the windows.

Before the drywall is installed, check the vapour barrier around the window, the vapour barrier should stop at the edge of the framing for the window. That edge should be taped with Tuck tape as tight to the spray foam as you can manage. This will help stop air transfer from the walls beside the window even after the drywall has been installed.

Check around the edge of the window with your hand, were you installed the spray foam. You’re trying to feel any drafts or gaps in the spray foam that you may have missed. This is your last chance to insulate, so add spray foam to anywhere you think there could use some more. Be careful that you do not add too much, remember that the foam expands. Once the foam has dried and you have trimmed away any excess foam that protrudes past the window jambs you can install your trim.

Once your trim has been installed and most of the painting has been completed you are going to want to caulk the trim. Caulk all the edges with as thin a bead of caulking as you can manage. This is the last step in stopping air leakage. Any air that happened to seep through all the other measures will be stopped here by the caulking. The trim might feel cold to the touch, but you wouldn’t have any drafts around the windows. The cold air will warm up in the walls from the furnace inside the house.

So if you do everything I have listed here you should end up with a draft proof window.

Rob Abbott

Operations Manager

Village Builders inc.