Tuesday, May 25, 2010

Larger Sunbox for MVHR

25 May : Having thought about this more, I could build the Heat Reclaim unit (MVHR) in the loft first with the air intake in the centre position between the present sunboxes, just below the glycol pipes.

This would be the right position for a later project to develop a tall centre sunbox with a ground level air intake, to use the 'stack effect' to help drive warm air to the intake. Taking this idea even further, the air intake could be moved to below ground, drawing air from pipes underground, for winter. The polycarbonate here could be double or triple skinned, to gain but not lose heat as it rises... or perhaps remain clear, because the rate of flow is too fast for significant heatloss.

The earlier idea, of a 1.3m wide sunbox, would need to evacuate this box twice a minute to maintain 0.6 ac inside the house. One that is 2.4 wide, covering the two small windows, would only require one evacuation per minute. During summer the polycarbonate in these can either be lifted off, or slid back.... Hmmm... I prefer to keep it to the smaller size.

This all takes time to think out and is a more radical intervention on the house, so needs to be done gradually. First an MVHR with intake on the south side....

This is becoming a bit like the Solarventi that my friend Karina has, although this is on a larger scale!
If the Solarventi can push through a good volume of air with such small boxes, perhaps the 1.3 m wide one would be enough. The Solarventi SV30 claims a throughput of 120m3 per hour, just right for the number of airchanges we need.
Hmmm..... something to think about.

25 May PS: Had a chat with my professor and he is strongly against MVHR, mainly because very few houses in the UK are airtight enough for it to really count.  If it is left on all year (it may need to be because the law requires that extract required for toilets) then it is quite an overhead if you haven't got PV to pay for the electricity. In our house, we would have it off from April to October, and just use the existing extractor fan. But it's an expensive bit of kit to use only from October to April. errr... however... our house is recently built, and a lot more airtight than most British houses. We could have an air leakage test done on it. The point about it being parasitic on the power supply for 6 months of the year is also worth considering.
   I also had a phone call with SolarVenti. I am interested that their units are only 100mm deep, but the 3m x 1m unit (SV30) can still channel up to 120 cu.m/hr into the house - so perhaps my proposed 5m high x 1.3m wide unit isn't so weird if I do it at all.
  Had a chat on the phone with David Atkins, and discussed the idea (above) added to which could be the idea of charging the ground under the air pipes, using the Sunbox mark 2.

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