61: Window Install

After checking around for where I could buy my windows, I came across a replacement window factory. These guys make the windows that people buy (and have professionally installed) when they want to upgrade their old, single pane windows. The factory has a “mis-measure” cage where they store and sell these windows at significantly reduced price ($75 each). These windows are all vinyl, double hung, low-E, argon filled, and best of all Energy Star approved in all 50 states. Comparable windows in Lowes and Home Depot sell for about $250 each (before installation).

I had gone to this window factory once before to look at their windows, and was disappointed to find no two windows the same size, or even same color. However, on the second visit, I found 13 windows in exactly the size and color I wanted. The sales rep accepted my offer of $50 each, so all my windows cost me $650. All the windows were still in their new plastic protecto-wrap, so I feel like I got a real bargain.

One characteristic of replacement windows is that they don’t have a nailing flange like “new construction” windows. You couldn’t install them (with a flange) unless you removed some house siding, which would make the install cost prohibitive. So, with no flange to nail through, you install them by running screws through the window jambs into the wall studs, and then caulk the snot out of the joint between the window and the rough opening. It helps that they make caulk in the same color as the window frame, so you won't notice it's there. My girlfriend had 12 windows replaced this way and the finished work looks good, even though I know there is a lot of caulk on each window.

Still, I don’t like the idea of having to depend on caulk to keep the rain out. Even if you use the fifty year (warranty) all silicone caulk, (like they did) I still don’t like depending on it. So, I needed/wanted a better install method to make me happy. What I “wanted” was a nailing flange like new construction windows.

One of the girlfriend’s windows is a bay window that has a center picture window flanked by two smaller windows. Where the windows join they used some type of “extender flange” to cover the joint. I asked the window factory rep and found out the flange comes in several widths, the widest being two inches. It has a feature on the back that allows it to lock into a groove on the edge of the window frame. I bought some and tried it out on one of the windows. It works beautifully. I am very confident it will yield a good, waterproof joint. Best of all, it gives me the flange I was looking for. It costs about $10 a window, so now I’m up to $60 per window.

I don’t nail through the flange; that would void the warranty on the windows. But, I do use it to seal and waterproof the joint between window and wall. Best of all, I don’t have to depend on caulk.

Pic one shows the flange. Notice how the flange goes “under” the Tyvek at the top of the window. Pic two shows the Tamko flashing material installed on the sides. The top piece of flashing hasn’t been installed yet.

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Note:
I have decided to finish each outside wall (housewrap, window prep and install, exterior trim and siding) before moving on to the next wall so that I don’t have to spend all my time moving scaffolds.

60: Windows Sill Pan and Sill Dam

Now that the roof is on I need to get the outside OSB sheathing covered up and protected. It’s been out in the weather for five months and is beginning to show signs of ageing. So, it’s time for housewrap…pronto.

Back when I built the exterior walls and sized my window rough openings, I had not yet done any research on the “best” ways to install windows. I have studied lots of houses being built over the years, but I’d never seen anyone put in a sill pan or a sill dam for a window. I didn’t even know they existed until a YouTube video pointed out the need and the benefits for both; so I had to lengthen my rough openings by ¾ inch. Fortunately, I didn’t have to adjust the rough opening width.

What is a sill pan and sill dam you ask? After installing the housewrap (some call it the Tyvek or weather resistive barrier) many people then cut the housewrap at the windows, fold the flaps into the rough opening and staple. They then just slide the window frame in and screw/nail it in place. They are depending on the window’s nailing flanges to keep out any rain that gets behind the siding.

But sometimes, rain does get behind the house siding and then the nailing flange of the windows. It then runs down the sides of the rough opening (the correct term is the window jambs) and pools on the window sill. It rots the sill out, then proceeds to soak the insulation under the window, rendering it useless, not to mention providing the moisture needed for mold growth. So, your utility bills go up, you get sick house syndrome and then a big repair bill to tear it all out and rebuild it. You think I’m exagerrating? A friend of mine has a neighbor who is having eight windows rebuilt right now (at considerable expense) for this very reason.

So, the sill pan is a waterproof layer that catches any water that runs down the insides of the jambs and along with the sill dam harmlessly push that water back outside the house siding where it will do no harm. There are several ways to make a sill pan. You can buy then prebuilt, but they are expensive (and none of the local stores stock them, so you have to special order). Or, you can make them using window flashing material. The material I am using is a foil faced, butyl rubber adhesive backing material made by Tamko. The roll is 6” wide by 100 feet long and runs about $13 per roll. Sticky doesn’t even come close to describing how well butyl rubber adhesive sticks to everything (including your fingers). So, if you use it, plan well and in advance of how you’re going to maneuver it around to install it.