What 3 steps will green your home’s building fabric?

To truly green your home you should work to improve the building fabric first. For older properties the 3 steps below will produce greater comfort, lower energy bills and lower carbon emissions by giving you a structure around your living spaces which keeps the heat you pay for where you want it  – in your home.

Step 1: Increase Air-tightness

Incense stick test for draughts

The incense stick smoke test for draughts – Be aware of the fire risk when using incense!

Air-tightness in buildings does not mean sealing yourself up in an airless plastic bag. It’s about getting the right balance of ‘intentional ventilation’ (essential for healthy buildings and people) and getting rid of ”unintentional ventilation’ – ie. draughts.

For example, wait for a windy day and hold a smoking incense stick by your letterbox or at the junction of your floors and skirting boards – under kitchen units too. Is the smoke going straight up?

You can green your home by tackling draughts:

  • Seal up the gaps you find with silicone mastic or other sealant
  • Draught-strip doors, windows, letter-boxes, keyholes and (hardest of all) cat-flaps
  • Install extractor fans (preferably with a heat recovery function) in ‘wet’ rooms such as kitchens and bathrooms
  • Make sure that roof spaces are well ventilated, but that all the ventilation stays in the roof space and doesn’t descend through the loft hatch!

Step 2: Install Insulation

After reducing heat-loss from draughts, insulation is next. In the UK, some 40% of each individual’s CO2 emissions are associated with space and water heating. This means that, if you live in an older property, there may be a real opportunity to make the some basic improvements that reduce your demand for space heating in winter. The less heat you lose via poorly insulated walls, roofs, floors etc, the less heat you have to put in, so your boiler, your bills and your CO2 emissions get smaller!

Most people have already installed loft insulation and, where possible, cavity wall insulation. But what about floor insulation or solid wall insulation?

Internal wall insulation

Applying internal wall insulation in between studwork.

Insulating Solid Walls

Insulating solid walls will cost you significantly more than cavity wall insulation. That said, it can often be done at the same time as re-decorating and is great way to green your home.

Insulation can be applied either internally, with a plaster or plasterboard finish, or externally, with a render or other finish. External insulation is generally recognised as the best method, but it can be significantly more expensive than internal insulation.

The choice may depend on your house type. In a terrace you might insulate the external wall on the inside to the front (so keeping the front facade the same as the neighbours) but use external wall insulation at the rear where planners are less likely to have any objections.

Much helpful advice is available from insulation manufacturers. Their technical departments can even calculate U values and assess interstitial condensation risks for you.

Part L1 (B) of the Building Regulations sets out minimum standards for refurbishment where more than 50% of a ‘thermal element’ (walls, floors, roof) is to be worked on. When insulating, look to exceed Building Regulations requirements whenever possible.

Insulation material considerations

Your choice of insulation materials will depend largely on 4 things: The price, ‘greenness’, thickness and Building Regulations.

Price: Some insulation materials (particularly glass-fibre) are heavily subsidised by the energy companies. More natural products such as sheep’s wool or recycled newspaper tend not to be, so some will cost much more.

Carbon Intensity: Think about your basic requirements first. If you don’t want to use petro-chemical based insulation this rules out polystyrene, phenolic foam and polyurethane, and even recycled plastic. If you want to know how much energy each product takes to produce, see the Index of Carbon and Energy (ICE) produced by Bath University to help you calculate this. Natural products such as sheep’s wool, hemp, cotton or recycled paper may be much more breathable and helpful if you need to control moisture.

Depth: In general, the better an insulation material is for a given thickness, the more expensive it is. It may also (such as with plastic insulation) be less environmentally friendly. Your choice will often come down to space. If you have to insulate internally the 3 solid external walls of a 2m-wide kitchen, you might meet Building Regulations with 65mm of foam board and plasterboard, or nearly 110mm of natural insulation and plasterboard.

Step 3: Improve Glazing

Easily-removable secondary glazing over a sash window in a 100-year old home.

Easily-removable secondary glazing over a sash window in a 100-year old home

Glass is not very good at insulating. Crudely, if you can see through it, it’s losing heat, but there is hope. A window which meets the Building Regulations is more than twice as good as a single-glazed wooden window, and with effort (and cost) you can get almost twice as good again.

New energy efficient windows

When assessing one set of windows against another, ask for the U value and enquire whether this is a ‘whole unit’, or ‘centre-pane’ U value. The latter is as it sounds – the U value at the centre of the glazed unit, without the effect of the frame itself, aluminium spacer bars and all the metalwork which modern, secure windows contain. A whole unit value tells you more, but at least ensure you are comparing like with like. The lower the U value, the slower the movement of heat across the pane and so the slower heat will escape through your windows in winter.

Remember that you need Building Regulations approval for new windows. A FENSA contractor can self-certify, but if anyone else fits them you must pay for a Building Notice from the Local Authority and have the installation inspected and approved.

New glass in old frames

In some circumstances, if you don’t mind a bit of joinery work, you can fit double-glazed units into your old frames. Ask your supplier for a unit which meets Building Regulations and consider the extra insulation value offered by filling the gap between the panes with Argon, an inert gas, instead of just air. Ask about ‘warm edge’ spacer bars too. These lose less heat than traditional aluminium spacer bars.

A ‘recipe’ for a Building Regulations-compliant unit is 4mm float glass, a 16mm gap filled with argon gas, 4mm coated glass with a soft-coat low emissivity coating, and warm-edge spacers. Approved Document L of The Building Regulations will change again in 2013.

Cheap alternatives

If you aren’t replacing your windows, draught-strip them so that no air gets in. Once you have done that, consider secondary glazing. This could be as simple as a cling-film-type plastic product, or joiner-made ‘bespoke’ units.

If secondary or double glazing is too costly, a good thick pair of curtains may help to limit heat loss and draughts. Make sure they don’t drape over radiators – tuck them up tightly on the window sill.

© Nick Parsons, Consultant and Trainer with Sustainable Building
October 2012

Also see:
MVHR system installation
Best insulation material
Boarding a loft over insulation
Cavity wall insulation work
Insulating a solid wall
Energy Efficient Windows
Underfloor insulation

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