Insulation - all wrapped up

Government carbon reduction targets and rising energy prices means social landlords are under pincer pressure to make their existing homes more energy efficient. As part of 24housing’s Retrofit Best Practice Campaign, Juliet Davies helps motivate to insulate…

Housing stock is often an eclectic mix of the styles of many eras – not only solid walls or cavity walls, but system builds such as no-fines, concrete panels, and even steel. And some post-war homes include huge plate glass windows designed to flood the properties with light – whilst losing all the heat.

The style soup means social housing providers face multiple problems in finding insulating solutions, but the answers to those problems may be easier than they first appear. Whilst myriad products are available for new-builds, retrofitting of energy saving materials to existing housing stock is not difficult.

BETTER IN THAN OUT
It’s a no-brainer. To ensure your properties meet emission reduction targets, the first thing to address is to prevent the loss of heat already paid for. Heat can leach out through every external part of the property; windows, doors, walls, roofs, and floors. Developing a housing energy saving strategy means assessing your stock - are the properties solid, cavity walled or even ‘non-traditional’? What percentage has double glazing? What thickness of loft insulation has been installed?

National Indicator NI 186 determines the per capita reduction in CO₂ emissions in each local authority area. It is estimated that each public sector home produces around 4 tonnes of CO₂ annually, therefore, to meet government targets, a programme of insulation would appear to be the first, and most easily undertaken, step.

WALLS
Wall insulation can comprise solid and cavity, internal and external insulation. Results vary, as does the difficulty of application. Efficiency is measured in “U-value” - how well a building element conducts heat.

• Uninsulated cavity walls can lose up to 35% of the heat inside.

Glass or mineral fibre, polystyrene beads, or urea formaldehyde foam installed within the cavity can save residents up to £115 per year, and approximately 610kg of CO₂ according to the Energy Saving Trust (EST) figures. Cavity wall insulation, being blown into the cavity via a series of small holes drilled externally, causes very little damage to the wall.

Cavity options include: urea formaldehyde foam which expands within the cavity and is installed via 20mm holes drilled around the property; blown mineral wool (granulated spun glass or rock wool) which is installed via 20-25mm holes, and EPS (polystyrene beads) which are introduced in to the cavity with the assistance of gravity so holes can frequently be drilled only at upper levels, and below windows.

• Uninsulated solid walls can lose up to 45% of the property’s heat.

Solid walls can be insulated externally or internally. External insulation can comprise renders, paints, and membranes, saving over £400 and 2.1 tonnes of CO₂ per year.

HDPE membranes can be affixed externally, and render applied to their impregnated meshed surfaces. Their ‘egg box’ style offers an insulating air-gap, whilst water proofing, and the render needs simply to add the required finish. Other systems are designed to be applied directly to the wall, with or without additional strengthening fabric.
Liverpool Mutual Homes (LMH) project at the Daneville Estate in Walton, Liverpool comprises of 600 properties including 63 voids. Using Structherm’s Structural Insulated Cladding they improved the wall U-value from 1.55 W/m2K to approximately 0.29 W/m2K, and produced a reduction in carbon emissions, reducing from a typical 8 tonnes to 2.11 tonnes per annum (per unit).

“We chose this system as we felt it offered several qualities that meet our requirements,” explains Dave Woods, Assistant Director – Technical Services, at LMH. “In the main, properties we chose to use the product on had major structural issues to the extent that they were un-mortgageable.

“This system gave the buildings back their structural integrity and stability; it also gives the added benefit of making the properties mortageable once more. Whilst the structural solution was obviously paramount, the thermal qualities of the product gave dramatic improvements to the thermal comfort of our customers’ homes”.

Solid wall treatments suit not just those pre-1920s properties – they could offer relief for the insulation headaches often associated with non-traditional build. Freebridge Community Housing in Norfolk recently insulated the walls of 850 Airey concrete block homes using Weber’s EWI system, a one-coat mineral render system providing a fast-track weatherproof finish over a thermal insulation panel. Tenant Darren Cross is impressed with the improvement to his home. “We used to have to run the heating up at 25/26 degrees just to maintain adequate warmth as we lost so much through the walls and windows,” he explains.

“Now we keep it at 15/16 degrees and it is still too hot! That 10 degrees saving will help keep our gas bill lower even as the prices go up. It’s never been this comfortable.”

• Internal insulation of solid walls saves an average of £380 and 2 tonnes of CO₂.

There are more drawbacks with internal insulation. The inevitable reduction in room size can cause problems in very small properties, or those with fitted furniture. However, internal insulation materials can be cheaper as they do not need the weatherproof properties of externally fitted products. Internal insulation boards can be applied with a ‘dot-and-dab’ method if substrate allows, or battens and insulated boards, or insulation and plasterboard.

• External insulation

Even a simple coating of water repellent or weather-proof paint can improve a wall’s U-value. Rain soaks in to porous masonry, and heat is lost as this evaporates. Pebble-dash cladding however, is more retro than retrofit.

WINDOWS
• Double glazing increases internal surface temperatures and reduces draughts.

Around 20% of heat can be lost through single glazed windows. Thermal transfer through frames can contribute to this figure. The ETS estimate approximately £135 and 720kg of CO₂ can be saved per year per property, and claim that if every property in the UK that required double glazing had it installed, the country would save around £700 million and “the equivalent of around 740,000 households' CO₂ emissions.”

At Dalrymple, Enfield, Boyland Joinery Ltd renewed around 1500 windows in 314 properties for the Origin Group. CO2 emission ratings were not specified as part of this particular project although the housing association chose WWA (Wood Window Alliance) standard wood windows for their thermal performance; their sustainability and because they are low maintenance. The best measurement to compare thermal performance of the original and replacement windows is the ‘centre pane value’. The original windows were single glazed with a U-value of 5.8wm2k. The double glazed units installed had a centre pane U-value of 1.7wm2k, a saving of 4.1wm2k. This does not take into account that the original windows were not weather-stripped, and therefore very draughty, compared to the double weather-stripped new wood windows.

Replacing windows in high-rise buildings requires additional security mechanisms, and a tilt/turn option for easy cleaning. At Taylor Place, the East Thames Group installed Technal’s FXi65 windows which can accommodate 17mm up to 48mm glazing units, allowing more economical glass specifications to be used, whilst still delivering the targeted U-value. A U-value of 2.2W/m²K can be achieved even with a glass centre pane U-value as high as 1.9W/m²K.

• Secondary glazing is an option for listed buildings, or within conservation areas.

Being cheaper to buy and install, it is also an economic choice if the existing frames are otherwise sound. Secondary glazing causes no damage to external brickwork or render, and minimal disruption to the tenant as the units are prepared off-site and fitting is clean and quick. Secondary glazing can be manufactured with wood, aluminium or uPVC frames, and, it is claimed, can reduce traffic noise by almost 80%.

LOFTS
The EST suggest a saving of over £150 and 800kg of CO₂ per year can be achieved when the recommended loft insulation thickness of 270mm is installed – without insulation up to 25% of a property’s heat goes up through the roof. Whether roll-out mineral wool quilts, blown cellulose fibre, mineral wool or pourable beads, loft insulation makes an easy and immediate impact on living conditions and energy savings.

REGULATE TO INSULATE
The Carbon Emissions Reduction Target (CERT) which came into effect in April 2008 makes it obligatory for every UK energy company to take necessary steps to ensure that the amount of CO₂ emissions from domestic properties is reduced.

“Many thousands of Social Housing lofts are being insulated as part of the CERT programme,” said Richard Moores, Vice Chairman of the National Insulation Association. “Housing Associations are carrying out this work as part of their Decent Homes Strategy and in order to reduce resident’s energy usage. Social housing landlords are able to obtain grants for this vital work through the CERT programme.”

BREATHING SPACE
Wrapping up well with insulation increases the feeling of warmth and reduces bills, but it can also limit air circulation. Ventilation must be addressed at all stages – if water vapour is still produced it needs somewhere to go, and condensation can form at any surface where there is a temperature difference. In extreme cases, even dry rot can be initiated when timbers have been affected by sustained levels of humidity caused by lack of ventilation.

INSULATION IN THE BAG
With hundreds of millions of pounds and thousands of tonnes of CO₂ to be saved, large-scale insulation projects are the essential basics of your retrofit programme. And with a range of financial sources including CERT, the Carbon Trust, and even the lottery (Community Sustainable Energy Programme), offering grant funding for housing providers, finding the right insulation is all wrapped up.