Mechanical ventilation - to use in summer or not?

Mechanical ventilation with heat recovery is great for the cooler months, you get that fresh air feel without having to open windows and without losing all that heat you've built up with your central heating.

The question is though, should you leave it on during the summer or should you rely on opening windows? If you leave it on then it is using energy to ventilate your home, although with a summer bypass function there will be no heat recovery. The other advantages include not having insects coming in to bite at night or buzz around your food, and it reduces the disturbance from the inevitable increased noise in summer - planes flying, children playing, barbeques in the garden.

But it does use energy and you could just open the windows to create air movement and a cooling effect.

The first year we had our system we kept windows shut and the MVHR switched on - we knew the horrors of a fly infestation and didn't want a repeat! In a hot spell it was quite hot in the house, but then it would have been hot if we opened the windows; the MVHR certainly didn't act like an air conditioner.

This year we are using windows and blinds during day to keep sun out and allow fresh air in; we're putting up with daytime insects. Once there are lights on in the evening we close all the windows and use the MVHR to ventilate the house and that's successfully kept away the mosquito bites!

We try to keep our electricity bills down in other ways, i.e. nothing is left on standby, broadband is turned off when we're not using it, we use a laptop rather than a pc and this is put on standby if not in use for more than 10 minutes and turned off at other times when not being used.

So maybe the MVHR is our electricity indulgence, along with the fridge/freezer and phone. However, used intelligently we feel it contributes to good ventilation of our home without excessive energy use.

Has anyone else out there had experience of using these systems in their own home?

Clever use of blinds and curtains

Curtains and blinds can help improve the thermal performance of your house - more information. Since having ours installed we have learnt a lot about their effectiveness.

The first big shock was the effect of having our house decorated over the period early October up until Christmas last year. We had approached the decorator in May, but that was the best time we could get. Anyway we didn't have any curtains or blinds at our downstairs windows for that whole period; also doors were left open quite a lot during the day and on top of that we had snow from November. All of that led to a massive increase in our use of gas - it came as quite a surprise.

We have noticed some real benefits of our blinds since then. We have a Luxaflex Duette insulating blind on our patio doors. This stops quite a lot of the cold air coming through that large expanse of glass - and it does come through despite being double-glazed. If we raised the blind first thing in the morning we could feel that cold air trapped between the blind and the window and that was then coming into the room. So what we've been doing is waiting for the morning sun to warm up that layer of air, then we open the blind. We can then make the most of the solar gain from the sun coming in through the glass and warming the room.

During very cold weather we often left the blind closed all day as it gives the room a nice light feel even when closed and it's kept the room that bit warmer. At night we add thermally lined curtains to keep the house even more cosy.

Also when it is hot or too sunny we've used the blind to stop too much heat coming into the house. Glaring sun can be excluded by partially closing the blind; too much heat coming in can be prevented by closing the blind altogether to prevent that solar gain. The room is still nice and light but it is a cool oasis when it's been really hot outside. When it is cooler outside at night we've raised the blind to reduce temperatures indoors.

We have a north window that has a Luxaflex Architella blind, which must be about the most insulating blind on the market. We keep it firmly closed in the winter, which definitely reduces the icy draught coming down our stairs! In hot weather we can open it to help us lose some of the heat indoors.

We are seriously thinking about having these blinds in other parts of the house as we are so pleased with how they have worked. If we have another cold winter we hope to also notice the difference in our gas bills - it's clearly not enough just to have double-glazing.