Renovating 1948 terrace

[dhaslam]

I wouldn't be too negative about alternative electricity suppliers.    When  new wind farms are set up they have to have a contract to supply electricity into the grid.  The  alternative electricity suppliers have  their own customers and  can offer contracts.     If every customer changed  over to an alternative energy supplier  it wouldn't mean  immediate change but it would greatly accelerate the  change.   

In any case direct electric heating is very efficient.  The heat goes directly to where it is needed  with no pipe losses etc.   Water based systems  lose quite a lot of heat in the  storage tanks  and pipe connections to the boiler.   

[Loir]

How far did you go in making your house airtight before you fitted it? Have you ever tried running with it turned off for a few days in winter to see what difference it makes to the feel of the house? I'm somewhat concerned as to how airtight I need to make the house before I'd notice any difference.

The major point is that, to keep the condensation under control, you need forced extraction from wet areas like kitchen and bathroom. This means expelling hot air from the house, wasting that heat.

An MVHR system will retain most of that heat and put it back into the house, reducing heat wastage. And it means a supply of fresh warmed air into the rooms.

My system is linked into other systems so is not easy to turn off. For example the pumped shower only works when the ventilation is running full power. Similarly the kitchen cooker hood. And we do most of our clothes drying in the airing cupboard which is, again, linked into the ventilation system.

Loir

[pdf27]

The major point is that, to keep the condensation under control, you need forced extraction from wet areas like kitchen and bathroom. This means expelling hot air from the house, wasting that heat.

Ummm... no, you need sufficient ventilation to ensure that the relative humidity in these areas stays below the critical value at which you start getting problems. What I'm trying to get a feel for is just how difficult it is to get a house sufficiently airtight that MVHR is required, from which I can make a stab at calculating the energy savings it will make compared to natural ventilation. If the practical airtightness limit is going to be 90% of the required ventilation anyway in most of the house, then I'm better off looking at improving the natural ventilation in most of the house and fitting single room MVHR systems in e.g. the bathroom.

[Loir]

I am just saying what I have done.

You have to decide if you need forced ventilation in wet areas of your house.
Then consider the cost of just expelling that heat.
And then the cost of a whole house MVHR system versus several individual room systems.

You may see the addition of warmed fresh air to living and sleeping areas as a useful bonus.

But the final decision is, of course, up to you.

Loir

[pdf27]

Indeed. Problem is, being a mechanical rather than building services engineer I'm finding it extremely difficult to find any solid information to base that decision on - and hence was hoping you had some relevant numbers you might be able to supply me with.