Can the Existing stock ever be Carbon Neutral?

[Anonymous]

Hi,

I was just wondering could the existing housing stock ever be carbon neutral using micro renewables such as Wind turbines and Pvs. The reason I ask is the SD Commission has a stat that 60% of our energy in homes are consumed in space and water heating which uses natural gas in most places so how could just a wind turbine or Pv ever replace the heating unless you change the whole heating system.

I know Solar water heating could help reduce this burdern and the above could try and reduce the electrical needs but I always had the idea that you only needed one microgeneration form. As I've conducted my research it seems clear you need a combination that suits your particular home.

Please correct me if I'm missing the obvious :-

[Anonymous]

Probably not is the short answer there. Unless some revolutionary design is come up with, sticking wind turbines on houses simply doesn't work very well due to turbulence, and we'd need to cover every roof in the country in PV's to even make a dent – which would cost a staggering amount of money, and require the national grid to be completely re-engineered. It is possible that a new generation of PV will be considerably more efficient and affordable.

In the meantime the only way we can get existing stock even close to neutral is by a lot of painstaking insulation work, although no matter how well eco-refurb is done, the results can't be as good as a well designed new property. It's a matter for serious debate whether or not our best bet long term would be to bulldoze a huge amount of old housing stock and start from scratch…

[David Olivier]

After 5-10 years of trying, Germany has essentially solved the problem of how to insulate even existing (most of theirs are solid-walled) buildings to Passivhaus standards. It's not rocket science, as the saying goes, so maybe in a few decades the UK will learn this precedes micro-generation and maybe in a few years the AECB will start to produce guidance in this area.

But let's walk before we run – as Paul says not even new buildings meet a decent standard. Also UK regulatory documents have led to abysmal design of most party walls (the Stamford Brook project) proved this, and the UK has defined air permeability so that the air leakage of a house is divided by total area (including party walls and floors). If the party walls and floors are airtight enough to meet Part E, the thermal envelope of a new flat or row house can then be incredibly leaky.

As far as I see the only way to get good standards is to self-build or use a small number of building companies and craftsmen which/who still pride themselves on their workmanship. They do exist.

David.

[Anonymous]

We do.

[Mark Siddall]

David,
You have mentioned that there were problems with the party walls at Stamford Brook a couple of time on this forum. What exactly was the problem?

Mark

[David Olivier]

Mark

They were empty cavity walls. The U-value varies according to wind conditions but apparently can go as high as 0.9 W/m2K. Air simply blows across the row of houses, through the cavity and out the other side.

Almost all new dwellings are built this way. The heat loss of attached houses is then worse than a detached house.

I saw some row houses in Sweden 30 years ago where the separating walls were a simple prefabricated sandwich element containing 100 mm polystyrene in the centre and concrete both sides. A cavity wall with 50-100 mm insulation and without ties also works perfectly well according to UK experience. Current practice appears to be based on people who wrote Part E never talking to people who wrote Part L.

David.

[Nick Grant]

And convection into the loft space I believe. Solved by closing the top of the cavity.

[Anonymous]

I wonder why there is a cavity? For sound insulation? My house shares a triple brick wall with the neighbour and definitely doesn't have a cavity. I'm now trying to work out how to include a peltier-effect cooler on the wall to transport some heat over 😉 (Joking of course).

Paul in Montreal.

[David Olivier]

If you close the cavity you may get too much heat or sound transfer – in low-energy houses (at least if they have individual heating systems) party walls should be insulated to reduce the heat loss to the house next door if that house is unheated.

I think it's a non-issue really and very easy to solve. It's only become an issue due to failures in government decision-making.

David.

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