In order the take advantage of the thermal mass of the existing solid concrete walls, and turn them into a heat store for the houses, we are building a new external wall and incorporating a large (250mm) cavity fully-filled with insulation between the two walls.  This significant layer of insulation will stop the heat absorbed by the existing solid walls transferring to the outside of the houses and being lost, as it does at present.

Before we build these new external walls, a couple of steps are required first:

1. Removal of the existing bays on the houses to make it easier to build a single wall right across the front
2. Addition of new foundations on which to build up the new walls

The video below shows the houses with the bays removed and the new foundations being laid.  The new foundations were combined with underpinning for the existing walls to make the overall structure more secure.

[youtube=http://www.youtube.com/watch?v=UjthbR13YcI]

The houses currently have solid concrete floors with no insulation underneath them.  As a part of the retrofit we are excavating these original solid floors, and replacing them with a combination of insulation laid under a new concrete floor.  Putting the insulation underneath allows the mass of the concrete to store heat and then give it back up as the air temperature in the house cools, thereby helping to keep the house warm.

Effectively the floor is then acting as a storage heater.  The heat absorbed into the floor is from a combination of passive solar gain and incidental gains from occupants, cooking and appliance use.  Basically whenever the air temperature in the house exceeds the temperature of the floor slab, the floor will absorb that excess heat.  The insulation under the floor slab stops the heat escaping to the ground below, storing it to be returned to the house as the air temperature subsequently cools.

The existing solid walls will act as a heat store in a similar way once the new external wall is built up with the insulated cavity outside the existing wall.

The video below shows one of the houses with the old floor excavated and Nick summarises our plans for the new floor.

[youtube=http://www.youtube.com/watch?v=yjePXnOUgKM]

Its an Aero chocolate bar in reverse of course!

[youtube=http://www.youtube.com/watch?v=tqivPdW6fE4]

(not that we’re endorsing a Nestle product)

We’ve now removed the chimneys from both properties; there are two key reasons for this:

1. They are no longer be required as the gas fires have been removed;
2. They are a significant source of heat loss.

This also makes it easier to fully insulate the party wall between the properties; this has two benefits:

1. It provides sound insulation between the properties;
2. It prevents heat being lost from the properties by being transferred through the wall up into the loft space.

It is often wrongly assumed that you don’t need to worry about insulating party walls, since assuming your next door neighbour is heating their house, then there will be no heat loss.  However, research has shown that heat will be transferred via the party wall up into the loft space and to the outside.  Insulating the party wall on both sides will prevent this from happening.

So that just leaves the question how will santa gain access on Christmas Eve?  Well, we’re guessing he’ll use the roof lights in the newly added sun space; its flat roof will be easier for him to park his sleigh on too …

[youtube=http://www.youtube.com/watch?v=pzAkUxNvKfM]