Silly! We are not talking about your belly button! We are talking about window installations of course. Around here in the D.C. area, we do not see Innie windows very often. In fact, I don’t think I saw any before we started thinking about the issue. Typically, you will only see them on really old houses, I saw them at Mt. Vernon this week! If you ask contractors or supply houses about how to do it, the most likely response is,”why would you ever do that? We wondered about that too.
Apparently, the debate has been going on for decades among building scientists and high performance home designers. Here’s what we are able to summarize.
Outie Windows: The glazing of the window is set flush to the outside of the wall
- Easier to install: They are installed by nailing flanges on the outer face of the wall
- Simpler drainage plane: No exterior window sill to worry about
- Deeper interior sill: Looks nice and you can leave a cup of coffee on the sill
- Conventional looking: Everyone has it installed this way
Innie Windows: The glazing of the window is set at middle of the wall
- Greater protection from severe weather: Innie windows are removed from the outer surface of the wall which protects them from driving rain and wind
- Better supported: Unlike Outie windows which are basically secured by the screws on the window flanges, Innies are secured and supported by the wood frame
- Solar shading: The recessed position of the glazing provides solar shading
- Better thermal performance: The glazing being within the wall’s depth keeps the glazing within the insulated thermal envelope
We chose to do Innie Windows. This means more installation steps:
1. Starting out with over-insulation of 1″ XPS on the head and jambs. This extra layer of foam adds R-value to the window frames.
2. Wrap the rough opening with Tyvak. The house wrap protects the home from damaging wind and rain.
3. Flash with Grace Vycor. We use this to build a water proof head, jamb and sill.
4. Install window. Using the expanding foam tape we previously blogged about to install the window to create an insulated, water-tight and air-tight seal around the window.
This is what our Innie looks like.