Wednesday, 6 February 2013

Where Is the Heat Going?

We're now six weeks after the winter solstice and the PV panels have started generating electricity again on sunny days. The solar thermal tubes have been sunk into gloom for weeks and refusing to heat more than the odd drop of water so presumably they are more prone to SAD than the panels. They also have less surface area too of course, which probably is a more accurate explanation for their inactivity.

This latest graph represents the data for the past year and shows that the house is repeating its bad habits of a year ago in its consumption of energy. The crimson line on the right side is just depicting the heat energy we are having to add. As the temperatures dropped outside in the autumn the house cooled and we started to add extra heat. This heating made no discernible difference to temperatures on the bottom floor, which continued to fall, but it did push temperatures up on the top floor and made the bedrooms over-warm.

If you are an engineer this may all make sense but I find myself baffled as to what is going on here. My understanding is that, basically, this house is a sealed box and we've seen the air pressure tests to show that it doesn't leak. The only way air gets in or out, when the windows are closed, is either by opening the front door or through the pipes going to and from the MVHR. So, dear reader, where is all this heat energy going? Some of it is clearly bouncing around at the top of the bedroom ceilings but, where is the rest of it? The MVHR is supposed to recover "up to 99%" of the heat in the pipes before it vents the stale air outside the building but, for the life of me, I don't know where it's hiding.

All I do know is that, at the moment, we are pumping extra heat into the house but the ground floor rooms are no warmer than a year ago. As Kermit the Frog sagely remarked, "it's not that easy being green".

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