Another hot summer Saturday, another day spent happily baking in the not-so-fresh air. There was a long walk in the morning before things got really steamy, then yard puttering, and then a lot of time on the patio with icy beverages & good books.

The birds enjoyed the feeder I refilled for them, and they were all over the birdbaths all day. Such happy little puffs.

And in an extra-fun addendum to the hot summer action, I did a nerdy self-challenge I called, "Can I keep the house comfortable AND avoid turning on the AC when it's scorching hot?"

Answer: Yes, sorta.

After some simple experimentation, I've found a way to keep the house cool enough we don't have to turn on AC, or at least don't need it on until after sunset when it's easier & cheaper to cool things down.

All I had to do was stop following the standard advice from HVAC and "how to keep your house cool" experts.

Okay, so. Let me back up a bit.

The Backstory

Spouseman, Mister Pips & I live in a 93-year-old brick bungalow. All that solid brick heat mass means it's dead easy to keep the first floor cool as long as the night temp drops under 72. At sunset, open windows with fans to cool the interior, then close up & pull down shades through the daylight hours. The temp rarely rises above 76F even when it's in the mid-90's outside.

The upstairs, now that's another story. The upper floor was originally a walk-up attic with a narrow stairway. It was finished ages ago, and now it's a finished space that accounts for 2 bedrooms and half the home's square footage.

But from a temperature control perspective, a vented, insulating airspace was brought inside the HVAC envelope. And as was typical when the remodeling was done, no provision was made for adequately venting the roof deck above the finished space.

All the HVAC & "keep your house cool in summer" advice says to keep ALL windows shut during the day, but when the upstairs is closed, it superheats as much as 20 degrees over ambient, which is really nasty when it's 90 outside. Not to mention hard to

We have zoned HVAC, so at least we aren't trying to cool the whole house when only the upstairs is hot, but if we're relying on the AC, the upstairs superheats up to 20 degrees over ambient by noon and sucks a lot of AC power staying at 80-82 through the afternoon.

Last fall I hung a curtain at the bottom of the stairwell, because despite the HVAC advice being "keep the air circulating" I hated knowing heat was getting sucked up the stairs and out of the framed upper story all winter. Heating bills went down, not up.

That brings us to the hot summer nerd challenge.

This spring when weather started getting hot outside (and upstairs) I decided to do more experimentation. Variables! Science!

After cooling the house overnight, I buttoned up the first floor like always, but instead of closing up the second floor, I left the northern and shaded windows open.

It worked a treat. Both floors seemed to be staying cooler. But. That was with temps in the 80's. Today was the real test. Up above 90F, only going to 70 overnight tonight.

Both floors were 68F at sunrise after being open all night. At 3PM, floor 1 was still 73F, and floor 2 was holding at 80. By sunset after 8PM, ambient was down to 83, floor 1 was 75, and floor 2 was 83.

WIN! The zoned AC took 2 hours to bring the upstairs temp down to happy sleep levels. (<74F) Or, to be entirely accurate, it ONLY took 2 hours. I keep thinking of how much harder the poor compressor would've had to work if the upstairs had been at 90+ instead of 80ish.

Anyway, I'm officially calling my new "vent the upstairs space whenever feasible " technique a success.

Other places to find things by me:

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