the proof is in the pudding

Today is a scorcher here in Portland, OR. By 4:30 pm the outdoors ambient is 96 degrees F. There were no clouds all day but the unrelenting parching sun. Tatyana has been out in the sun all day and I went and checked at 4:30pm to see how did my solar gain mitigation measures fare.

Here are the mitigation measures:
1) 4.5" diameter 320 mA computer fan on shade side of upper wing window

2) homemade silvery fabric exterior sun shade - see next photo


3) reflective foil behind driver side picture window

4) reflective foil behind sunny side upper wing window - top circled

5) reflective foil inside big skylight (skylight closed and factory shade open as in picture)

6) reflective foil inside bath small skylight (with skylight open in the middle (lockable position) of the 3 possible positions).

for comparison I use my all white Land Rover for comparison - picture taken at 4:30pm

the Land Rover only has a reflective inside front sunshade

Here are the measurements:

• ambient air in the shade at 4:30pm is 96F
• driveway concrete in the shade is 91F
• driveway concrete in the sun is 135F
• blacktop roadway in the shade is 99F
• blacktop roadway in the sun is 138F
• tatyana's upper berth mattress is 106F (I use this because it is a very high point just short of touching the upper fiberglass roof which is expected to have a boundary of very hot air near the surface)
• tatyana's black louver in the sun is 136F (very close to blacktop in the sun)
• Land Rover's console at the radio (still in the shade by the inside sunshade) is 126F

The internal ventilation in Tatyana consists only of the 360mA fan pulling air in from the shade side of the upper wing window, and the cabin air exhaust through the bath skylight set at the middle position. I am very happy to see this result - only 10F rise in a near 100F ambient in direct sun.

how about the house in a hot day?
Somewhat related. How about the house? Anticipating the very hot day today, I let the house vent in cool air all night. I am getting very good now in the procedures to keep the house cool during hot summer days. Typically in days like this the house temperature would continue to rise (due to latent heat transfer) slowly well after sun set. I only open the windows and sliding doors once the interior temperature meets the exterior temperature. At 8:30pm now the outside temperature has dropped to 82F, the interior temperature is only 72F. I measured the interior temperatures at three different rooms and they are within about 1 degree.

The reason the 1965-built house can maintain such low temperature is mainly due to 3 factors:

• it has very wide eaves in three sides
• i chose a very light color for the exterior sidings
• it has white membrane roofing

On the other hand on the entire back side of the house there is an expanse of 52 feet of single pane glass walls.

Even though I have 2 mini-split air conditioners it is not uncommon they receive less than 20 hours of use even in the hottest summer here.