Wednesday, November 13, 2013

A Window into the Architect's Process

While the framers are busy building floors next door, I am reviewing the window schedule at my desk. This house has around 28 windows, and I had to review them and revise some of them.

The building code requires windows in habitable space. There are requirements for natural light and natural ventilation. There are requirements for emergency egress. There are requirements that the actual window unit installed meets certain energy standards. These requirements must be balanced with the aesthetics from both inside and outside and with the function and use of the spaces.

Excerpt from SECTION R303
All habitable rooms shall be provided with aggregate glazing area of not less than 8% of the floor area of such rooms. Natural ventilation shall be through windows, doors, louvers, or other approved openings to the outside air. Such openings shall be provided with ready access or shall otherwise be readily controllable by the building occupants. The minimum area to the outdoors shall be 4% of the floor area being ventilated...

There are exceptions (like bathrooms) and special rules for adjoining rooms. It is not a coincidence that the area of light required is double the ventilation area required - think of a "double hung" style window (typical in the Northeast)It offers twice as much light as ventilation. We like light in our homes. Architects like to use a lot of windows. Designs today generally do not have a problem meeting these requirements.

Excerpt from SECTION R301
Basements with habitable space and every sleeping room shall have at least one openable emergency escape and rescue opening... they shall have a sill height of not more than 44" above the floor.... minimum net clear opening of 5.7 square feet... minimum net clear opening height shall be 24"... minimum width shall be 20"... shall be operational from the inside of the room without the use of keys or tools...
The three bedrooms on the second floor of this house each need an egress window. This architectural style typically utilizes double hung windows, but with only one sash - bottom or top- opening, a double hung window has to be excessively large to meet the clear opening area requirements. (this large opening is to accommodate a fire-fighter, in full gear, climbing in to rescue you). Such a large window would look WAY out of proportion, especially on the second floor, so architects have a trick. I specified one casement window, the same size as the double hung windows in the bedroom and with a lite pattern to match. (so it has a horizontal band across the middle, to make it look like two sashes) A better proportioned casement can meet the egress dimension requirements, because the whole window swings open from the side.

Windows are so important in our buildings for views, light, air, and safety. I hope this post gave you a "glimpse" into some of the things an architect has to consider. We'll talk about the energy efficiency of windows in a future post.


  1. Christie,
    Have you looked at the LEEDS certification requirements for mom and dad's new home ( It would be really cool (or warm or just right) if your new house next door could be rated that way.

  2. Rather than LEED, I elected to follow Energy Star Standards in the design and construction, and do it without the third party certification. (mostly to save the cost and hassle of it) LEED focuses on lots of "green" practices, like using local materials, building near public transportation, reducing on-site waste. Energy Star focuses more on creating a building that uses less energy to run. In the long run, while we all like to recycle and use earth-friendly materials, the best way to minimize one's environmental impact with one's home is for it to be super energy efficient.

    1. I think we both have a good understanding that mom and dad will follow through with every energy efficiency that you have made available to them. What a relief to know that they will be in more practical home. We all loved their house but what a struggle it was to keep up! I do hope you get sufficient credit for having put all this together for them.

    2. Thank you so much for your kind words, dear (anonymous) sister-in-law! I do hope once mom and dad are used to less stuff and a smaller space, they can be happy in their new, comfortable home.

  3. Thanks for sharing such a great blog... I am impressed with you taking time to post a nice info.
    Windows And Doors Phoenix