Practical refurbishment of solid-walled houses - INSULATION!

[chris]

I haven't have any figures to hand (we should try to get some for Sheffield) but much of the cities housing stock was built in an era of coal and horses and is now heated with gas, we need to refurbish and insulate it to the extent that it doesn't need heating (or as close to that as we can get).

An excellent document, CE184, on the practicalities of this from The Energy Saving Trust:

Practical refurbishment of solid-walled houses (CE184)

Our society has become increasingly dependent on fossil fuels such as oil, coal and natural gas. These are finite resources, having been created by natural processes over millions of years. Burning them to produce energy results in emissions of ‘greenhouse gases’, including carbon dioxide (CO2). These gases trap solar radiation in the earth’s atmosphere and cause undesirable changes in the climate.

Home energy use is responsible for over one quarter of all UK CO2 emissions. Today, about one in five homes in the UK have traditional solid brick walls. This was the main form of construction until the mid-1930s. In addition to this there are a number of other solid wall construction types, including systems using no-fines concrete and pre-cast concrete panels.

Current estimates suggest that approximately two- thirds of the dwellings we will be occupying in 2050 are already in existence. Improving the energy efficiency of these existing dwellings, including those of solid wall construction, will play an important part in achieving the UK Government’s CO2 emission targets.

By following the Energy Saving Trust’s best practice standards, refurbished housing will be more energy efficient and emissions will be reduced, thereby cutting energy consumption, saving money and safeguarding the environment.

Aimed at architects, builders and specifiers, this guide offers practical guidance on the most appropriate methods for the energy efficient refurbishment of solid-walled houses. Performance targets as well as installation details are provided for floors, walls, windows, doors and roofs. Additional issues such as draughtstripping and wider environmental considerations are also considered.

http://www.energysavingtrust.org.uk/dow ... =1&pid=878

There are more documents like this from the Energy Saving Trust on there web site.

There is an interesting thread that mentions CE184 on the Green Bulding Forum which includes some comments from Nick Parsons who has been involved with the South Yorkshire Energy Centre.

What is happening in Sheffield about this issue and what can we do about it?

[steve]

Another good site for information on altering existing properties is The Yellow House.

This site tells the story of how we turned our 1930s ex-council house into our environmental dream home. We wanted to reduce our energy consumption by two thirds and renovate our home using sustainable materials, but without losing comfort or style.

There's a a whole section on insulation.

As someone said at the last Nether Edge screening, it would be good to have one room that doesn't require any heating at all: thus survivable in the event of power cuts. How possible this is I don't know but you could certainly insulate one room to a very high standard.

[Gordon Ferguson]

The Yellow House people were lucky - they were able to use the best solution for walls - external insulation. For those of us in 9 inch solid wall terraced houses, you would need to get the whole terraced row done as one job. There are twenty two in our row...... but this could be a terrific community building exercise if you could get everyone to agree.

However, internal wall insulation to even current regulations, never mind wanting to be future proof, is highly problematic from what I have been able to work out. This is because what will happen is that the solid wall will be more or less the same temperature as the outside, which means moisture will build up in it to more or less to the same level as our damp climate - really bad for the north facing wall. This means that anything wooden in the wall will be prone to dry rot, and this is really really so not good.

In old terraced houses, the joists go half way into the solid wall, so one day your floor would just collapse unless you took remedial action. You would need to provide a ventilated air gap between the wall and the insulation, remove all the plaster and the floorboards beneath the insulation and cut the joists out of the wall and wrap with plastic and put on metal joist hangers. You would need to put the insulation into the ceiling void between the ground and first floor, and seal the whole thing from any moisture penetration from the rooms. This last is vital - the 'dew point' for the wall - where condensation will form - will be more or less on the inside surface, so any moisture from the rooms will condense on the inside surface and run onto the wooden floor and joists.

To me it looks like the long and the short of it is that you would have to trash your house, loose lots of valuable space, loose the benefits of 'thermal mass' - heat retained in walls - so a room gets unpleasantly cold as soon as someone opens a door or window, pay lots of money or spend lots of time, and at the end of the day you might not do it well enough to avoid rot anyway.

If anyone out there can prove me wrong, or suggest alternatives, I really want to know because I like living in a warm house, and the only alternative I can see is to learn to live in a cold one. Never mind the problem of the millions of such houses we have in this country.

Putting some insulation on the walls, such that some heat gets into the wall to keep it dry enough is an option. In our house, the ground and first floor joists run from side to side, so protecting them from damp walls will be easier. I am going ahead with roof insulation more or less to current regulations. I am hoping this will make a big difference, but I fear that getting the roof right will just draw attention to the cold walls.

On a postive note, I have developed a way of getting traditional sash windows triple glazed within the existing frames, so that you can hardly tell from the street. At the moment I have secondary glazing - there is no point going for triple glazing until the walls are sorted.... but anyone who is interested is welcome to come and have a look - 31 Rossington Road S11 8SA.

[chris]

I agree that the ideal solution is external insulation but, as you have said this isn't always possible and there is a risk with internal insulation that condensation will form on the cold, internal, face of the original external wall and cause serious problems -- interstitial condensation.

This can be avoided with a good vapour barrier on the warm side, behind the plasterboard, but the detailing is important and care has to be taken not to puncture it doing things like putting up pictures.

Following a thread on the Green Building forum I found some software you can download to check for the risk of interstitial condensation, BuildDesk U, however I haven't tried this.

I have found a free online U-value calculator but it doesn't do condensation risks.

I remember reading somewhere that the thermal mass provided by a layer of plasterboard is enough thermal mass for a room.

[Gordon Ferguson]

Chris,

Many thanks for the info. The building inspector was indeed not correct in the example from the Green Building Forum you cite. However, this was a roof and I am much more confident about the behaviour of roofs.

I have downloaded Buildesk and intend to have fun using it.

As for interstitial condensation, everyone rightly is very concerned about moisture from the *inside*, but I cannot find anyone talking about moisture from the *outside* - except as problems that can be remedied such as rising damp, poor pointing and failed gutters and the like. CE184 does talk about the need for an air gap:

”High exposure locations will need a small cavity
behind the dry lining. This will create a break in
any moisture transmission path and reduce the risk
of future damp. It is important to consult with the
manufacturer to ensure the correct adhesive is used.”

-along with the usual ‘get out of jail free card’ of telling you to talk to the manufacturer.

The reason why I am very ‘conservative’ about this is from bitter experience with our previous house.

Here is my story:

Our previous house was a mid-terrace in east Sheffield, bought in very poor condition for next to nothing. We even got a 120% mortgage on the basis that immediate remedial work would substantially increase the value of the property. It was six months before we could even move in, and I did most of the work myself.

Shortly before selling the house to us, the previous owner had had an ‘insert’ window fitted into the front facing bedroom sash window frame. Like everything else in the house, the job was very badly done. The wall faced south west, down a slope, so received no sun for several months through the winter.

After completing the purchase, Chriss, my wife, noticed that the skirting below this window was badly curved outwards. It fell to pieces in my hands, being held together only by the thick paint layer.

It turned out that the work on the window had allowed a very small amount of rainwater to get in behind the wooden window frame sill and then the stone sill, dampen the inside of the wall behind the plaster and then the skirting board and the wooden beams holding up the wall above the bay window in the front room below. They were riddled with dry rot, which was also in the wall all round the stone sill.

If this has been found by the surveyor, the house would have been rendered effectively worthless, and the people we bought it off unable to finance any repairs. A full specification repair would have required the replacement of the entire bay window and its roof, the beams, and a third of the bedroom floor – the joist ends went into the wall and the wooden beams. Regulations state that all wood within 1 metre of the furthest visible extent of dry rot must be replaced.

Since I did the work myself, I noticed that the joist ends and the bay window frame were clear of rot, and on the basis that they were considerably dryer than the surrounds, left them – though not without dousing them with liberal amounts of extremely dangerous chemicals. Despite its name, dry rot still needs some moisture in the wood before it can attack it. Seventeen years later they were still OK.

However, the wooden beams had to be replaced with concrete ones, the wall rebuilt, the bottom of the bedroom window rebuilt, substantial amounts of plaster hacked off and replaced, the bay window roof rebuilt, and the fancy cornice in the room below replaced.

What would a builder quote for all that today?

However, I am not daunted - I even dry-lined that wall eventually - with a good vapour barrier of course. I am now looking at internal insulation to the front of our current house, and external at the back - more later.