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
LIGHT, VENTILATION AND HEATING
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
EMERGENCY ESCAPE AND RESCUE OPENINGS
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.

The Letter of the Day is "F"

Frost on the Framing this morning! Today was very cold all day - honestly I cannot imagine working outside all day in temps like this- but Scott and John did it. And they Finished the First Floor!

If there was a sound of the day, it would be a loud BOOM. This was the sound that rang out periodically as the guys aligned the edge of each 4' x 8' sheet of 3/4" plywood (read: HEAVY!) against the previous sheet and let it fall into place.

Yesterday they had finished installing the floor joists and girders and steel columns in the crawlspace. We'll look more at how that all fits together in another post. The crawlspace is covered over now, with the only way inside through the opening in the back of the foundation. There will be a floor hatch, but they've decided to frame that later.

Sill plates are next, and marking out the interior wall locations. If the plates around the perimeter look "skinny" to you, it's because the exterior walls of this house are going to be framed with 2x4s instead of the more typical 2x6s. The framers commented on how infrequently they build exterior 2x4 walls. I made this decision while detailing the wall section to energy star standards. (using "CI" or continuous insulation) With the continuous exterior rigid foam insulation these walls will have, we don't need so much cavity insulation between studs, so using less wood makes sense. Continuous insulation performs better for many reasons than cavity insulation alone. With it's air sealing and insulation details, this will be a snug house. Next year, when the cold fall winds blow like today, my in-laws will be warm and toasty inside.

Sill Plate

So far the construction has been all about moving dirt and pouring concrete, but this morning, the excavator back-filled the soil around the foundation, loaded up his machine, and drove off. The lumber yard made it's first delivery of wood to the site and the framers arrived to start building on top of the foundation that has been constructed.

First Scott connected a heavy duty wire into the electrical panel in our basement, and ran electricity next door for their tools. This was decided upon so using noisy, expensive, gas-powered generators could be avoided.

shims ensure a square and level floor

They worked to clean up the top of the concrete foundation wall with a broom. They rolled out foam sill sealer that acts as a barrier between the concrete below and wood above. They drilled and installed the 2x8 sill plate, which is the first piece of wood placed onto the foundation and is pressure treated for that reason. Pressure treated wood can resist moisture better than regular wood, and concrete in the ground can wick moisture, hence the treated sill and the foam it sits on where the two materials meet. The bolts sticking out out of the top of the foundation wall go through the sill plate and nuts secure the foundation and wood together.

Next the rim joist was installed around the perimeter. This is a 2x10 on edge (it is whatever size the floor joists will be). All this work is really precise, with the guys checking the diagonals often to be sure the base of the building is square, using a laser level and shims to adjust when needed to make the top of floor level.

After the rim joist was installed all the way around the perimeter, the first center girder was installed. In this case, it's an LVL -engineered lumber - stands for "laminated veneer lumber" and in the photo it is more a medium brown than the dimensional lumber, which looks almost white. The girder sits in the beam pockets in the concrete walls and is supported in the middle on concrete filled steel columns (that are red) that rest on the thickened footings that were poured with the slab floor. The girder is what holds up the floor joists, and this afternoon before they left for the day, they had installed a few floor joists that rest on that LVL and cantilever out over the foundation wall to create a bay window in the dining area.

cantilevered floor joists

The Slab

This afternoon the slab was poured inside the house. Last week, back fill and gravel were placed inside the foundation walls and compacted. The interior footings were located, formed, and reinforced with steel. Speaking of forms, you can see the tall wood blocks sticking up out of the wall. They were placed there before the foundation wall pour to create a space for a structural floor beam to rest. That's called a beam pocket. Perfect example of how things that need to happen in a later stage of construction need to be coordinated earlier, as well as how the different trades need to coordinate.

A thick poly vapor barrier is laid down under the entire slab to prevent moisture from the ground entering the slab. If reinforcing is being used, it would be placed. This slab does not have any steel reinforcing in it. The concrete trucks delivered concrete that had fiber reinforcing in the mix, and this will replace the steel mesh that usually helps strengthen concrete. Because this is only a short crawlspace and the space won't be used for mechanical systems or storage, the slab is what is called a "rat slab". I don't know how it got that unbecoming name, but it just means it's 3" thick instead of 4" and possibly made to less stringent standards than a slab that needs to withstand a lot - like in a garage. Remember this slab is essentially on grade, so no drainage was necessary, either.

I wasn't around to see the masons "float" the slab, but they had some amazing equipment - like a float with a 20' long handle and a gas-powered float. Those tools, and their skill, allow them to finish the slab to be durable and have a smooth surface - floating the fine aggregate to the top without bringing too much water to the top.

Waterproofing

 Today was an exciting day at the new house next door. This morning I met June, of Hudson Valley Rubber-Wall; it's always great to see another woman on the construction site! She and her assistant sealed the exterior face of the concrete foundation wall with a rubber coating. Concrete is very absorptive, and when located underground, it can wick up moisture, so we apply a barrier that helps prevent water migration from the ground into the wall (and into the building). In the past, this barrier would be made of asphalt that was sort of painted on thick and messy, but spray-applied rubber is a much greener and more sophisticated approach. (literally green, too!)

After daubing at the clip spots and then spraying the entire surface of the walls, they applied 2" exterior rigid insulation to the outside of the foundation wall. This is also exciting to me because I detailed this house to have a super-insulated "building envelope" (the line between conditioned - or heated - and unconditioned space). It used to be that basements and attics were left "unconditioned" - it is that way in my house. But smart, modern detailing includes the basement, crawlspace, and attic within the building envelope. This allows for the insulation and air barriers to follow the exterior surfaces (rather than a house that, for instance, has insulation in the ceiling of the basement, trying to separate that space from the heated space above, without success). Much smarter for many reasons that we will discuss in the coming months.

2" thick R-10 foam