One of the problems of building a highly sealed house is the issue of getting fresh air into the house. The latest UK building regulation mandate how many ltrs of outside fresh air should go into a house based on size and occupancy, but also allow for specialty systems. As my application for building came in before these requirements I do not have to comply, but where I can I like to meet or exceed building regs. For outside fresh air I have added a C02 monitor from www.telaire.com. This monitors C02 and if above 1000ppm it actuates an electric damper, which allows the UNICO system to suck in fresh outside air as well as returned air from the house. This way I only heat outside air when I need it. In practice I have found that the damper needs to operate far less frequently than I expected, so I'm really glad I took this road, rather than simpler 'punch some holes' in wall approach.[Later Update - In practice I've found the ventilation requirements to control humidity mean that a CO2 monitor is not required. But I'll post more on this later]
Humid air from Bathrooms and kitchens will be extracted when needed via a passive heat exchanger. I looked at the active exchangers, but the initial investment, complexity and running costs did not seem to stack up. I've yet to hear of a satisfied customer for these things and the 90% heat recovery claims in the brochures may be true in the lab, but in practice the experience seems under whelming.
In the summer you can see from the picture that the two folding sliding doors can open so the roof acts more like a shading canopy. For extra cooling I can also blow in cool air from the shaded north wall (brick wall with single window in the picture) using the HVAC (where AC stands for air cooling :) system. The picture also reminds me I have one more folding sliding door to go - just need some energy!
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