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Energy efficient house but not stuffy

We’ve been making  a lot of effort insulating and sealing up our house in order to save money on our bills and reduce our CO2 emissions….so there is no point punching lots of holes in it in the bathrooms and kitchen….equally we don’t want a damp and (smelly) house. One option would be to install a whole-house mechanical ventilation with heat recovery (MVHR) system and another is to install individual room heat recovery units in the key areas.

Both work on similar principals – exchanging heat from moist smelly internal air to the fresh outside air as the first is expelled and the second is introduced into the house. They do this by passing them through heat exchangers.Picture

The system I am going for constantly monitors the humidity of the internal air.  The humidity level can be set for difference rooms.  when the humidty is below the setting the fan runs at its trickle speed of 19m3 per hour and when it is above it runs at 38m2 per hour.The trickle uses 9Watts (and 21dBAs noise level) and the boost 46Watts (and 45dBAs). They can also be installed in damp bedrooms as they come with a light sensor to stop them going onto boost mode at night.It’s claims are a heat recovery up to 86%.


PictureEssentially the extract unit looks very similar to a normal extractor fan but there is a bit more technical stuff inside – filters and heat exchangers.We are going to be putting in four.  One in each of the main bathrooms and ensuites and one in the kitchen.


The only other component is the isolating transformer unit that also has the humidity sensor and boost override cord.  This is positioned away from the unit so it can get a more accurate reading of the humidity in the room – useful when the SELV fan is installed in a shower enclosure.The whole units cost a bit more than a normal extractor fan but a mixture of the savings and importantly having a comfortable damp free house will make it a worthwhile investment.

Running costs
I’ve estimated that the running costs of the four fans will be around £48 a year if we didn’t have a PV system.  With the contribution from the PV system and the fact that the boost Wattage will not be on at night I estimate it will cost us around £27 a year in electricity.In terms of heat energy, they will of course lead to greater heat losses than a totally sealed bathroom/kitchen but the realistic would be a 0% heat recovery normal extractor fan which would lose a lot more heat. I’ll calculate the heat savings over a normal extractor fan in a follow up posting when I install them.