These are some additional notes from Gordon as he learns how to manage the temperature of the large thermal mass to both maintain comfort and reduce winter heating bills. From Gordon:
Regarding my material that I passed to you, specifically summertime temperatures, I said that the temperatures were stable. This is generally true, but not entirely.
A more accurate description is “comfortable”.
One half of concrete is fully ‘interior’ so generally reflects the interior temperature – both winter and summer.
The other half of the concrete is next to the exterior foam insulation Buried in the spreadsheet is the fact that over the ‘six months’ of winter ’09, this concrete dropped about 10 to 11 degrees F. For the period of ’winter’ when the exterior concrete is higher in temperature than the desired ambient – this is an asset, and helps heat the house. During the latter half of the winter, it is plainly a liability! I hadn’t really thought much about that early on so didn’t log wall temperatures to any extent.
So when it comes to the ‘summer six months’ – I’ve really just got a “learners’ permit” on how to operate the house! I want the interior to be comfortable at all times. However it is beneficial if I gradually allow the interior temperature to gradually rise so that the outside walls gradually warm up – hopefully to a temperature well above 70 F, preferably 76 or 77 F.
If I have open windows at night only I can slow the process, and the interior temperature is quite stable. I have been leaving some windows open all day every day, until now to allow the warming process to occur. Current temperature is about 75 F in south half and 73 in north wing. So the interior temperature has been rising at about 2 ¼ degrees F per month since early May.
The concept of rejuvenating the thermal battery is simple – but, non-trivial I’ve found.
Spring was cooler than normal, so was June and July – quite significantly. Summer really started Aug 1 and today hit 99 F! Being cool, I didn’t want to miss out reheating the outer walls so probably allowed it to warm a little too quickly. Normally, summer temperatures here peak the first week of August. It now seems summer is finally under way – for how long, who knows?
Bottom line for others interested in trying this type of retrofit - the savings in winter heating aren’t all “free”. There are some summertime operating considerations. If you don’t warm up the walls, you pay extra during the winter. If you try too hard, late in summer it could be too warm inside. You can’t predict the weather, so one is never quite sure where you stand.
As I said, I’ve got a “learners’ permit” J