The use of sand is questioned given results of the "sand under concrete slab" search I did. Nonetheless, it is required per California Building Code.Some other tasks completed today:
- The remainder of gravel was spread in the utility room.
- A vapor barrier was placed over the gravel in the utility room. Insulation is not required because the room is not heated.
- Sand was placed over the vapor barrier in the utility room.
- 5 inch diameter joles were drilled at the top of the 1st course of APEX block at every other vertical core where a rebar will connect to the concrete slab – see pic above.
- Big Creek Lumber dropped off the window buck material – see vid below. The window bucks for my home are pressure treated 3X8 douglas fir beams that will frame the window and door openings. They provide a stable surface to attach the windows and doors.
Green comment for today:
When designing a home in a winter heating season climate, place the majority of properly shaded window surface area on the south wall in the northern hemisphere, and on the north wall in the southern hemisphere. This will take advantage of free winter heat from the sun. This is one of the fundamental concepts of Passive Solar Design. Start with a value of 50% to 75% of your total window area. Then use a building energy analysis tool like HEED to compare designs with more and less window area with your starting point. You will find a percentage that provides the lowest heating energy need annually. This percentage is the most thermally efficient for your home. There may be reasons other than energy efficiency to increase or decrease the window surface area, but at least you will have a starting point to deviate from.
Thanks for reading. Please leave a comment if you like.
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2 comments:
Hi Mike,
Just out of curiosity, why a slab floor vs. other possibilities? It would seem that a raised floor could be insulated better and perhaps have lower embodied energy.
Thanks for the blog; it's fun reading!
Tycho.
Tycho,
Great question. It comes down to thermal mass, aesthetics and climate in my opinion.
For my home, 5 inches of concrete resulted in a minimum on the heating energy versus thermal mass curve. As a point of reference, dropping to 4 inches resulted in a 20% increase in heating energy. The additional inch of concrete stores enough heat from the sun during the days to prevent turning the heater on 20% of the time during the nights.
I like the look of stained finished concrete floors. Concrete can be poured over a raised floor, but the thickness is usually 2 inches without adding significant structure to hold up the weight in our earthquake zone 4. My floor will have higher embodied energy than a raised floor initially. However, over the full life cycle of the home, I think the annual heating energy savings will offset the initial energy input.
Finally, the Santa Cruz climate is very benign. The soil temperature is about 55 degrees all year long, with little variation. If I designed a home in a freezing climate, a raised floor would likely be a better choice.
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