Carbon Legacy Ltd


Woodgate Farm

East Leake



LE12 6Pw

Self Builders

Self-Builders and Property Renovators

Many people think that going green is a laborious task that costs the earth. But in reality; altering a few things in your home and the way you do things, will reduce your annual energy consumption costs dramatically. It’s all very well installing a £24,000 heat pump system; but without taking the necessary steps to reduce your buildings heat-loss, it may well be a unacceptably expensive to run system you’re investing in.

We have put together some tried and tested things to consider that many home owners often overlook. Please remember the “Fabric First” Improvement building philosophy applies to both new and renovated properties. The more you spend on insulation, the smaller your heat loss will be and the smaller/cheaper your Renewable Heating system will cost. Plus you will have lower bills for ever!

  • Air Leakage

    Achieving an airtight property requires a lot of care and attention to detail during building works but figures of 2-3 are achievable without major expenditure as long as all gaps are filled as the works progress with the generous use of expanding foam and careful filling of all joints/service entry points etc.

    Also, wet plastering is one of the best ways to ensure airtight masonry walls. Current regulations ask for a feeble target of 10 and new regulations due in 2022 should reduce this to 5. Timber frame houses use different methods to achieve air tightness including membrane’s and a lot of special sealing tape.

  • Cavity Wall Insulation

    Installing cavity wall insulation is one of the most cost-effective ways of reducing heat loss in existing properties.

    Many homes built after 1920 were constructed with a cavity between the outer and inner walls, these cavities significantly helped reduce damp and keep houses warmer than the single skinned walls that predated them, but there are still improvements to be had.

    By filling the cavity with an insulating material such as polystyrene beads or mineral wool you can retain as much as 33% of the heat that would have previously been lost through the cavity, and it’s all relatively simple to do.

    Holes will be drilled into the wall by the installation team who will then pump the material into the cavity, this all sounds quite a major job but in fact is quite straight forward and a such is a relatively low cost method of gaining significant savings for less than £1,000.

How Will it Benefit Me?

Over and above the significant savings on your central heating bills you will also notice that your home will be cooler in summer, all due to the improved insulating properties of the walls, it will also help reduce condensation on the walls and ceilings and provide a more stable and even temperature throughout the home.

Is My House Suitable?

There are two steps to see whether your house has a cavity wall. The year that your property was built will give you a good indication:

  • Before 1932 your house is unlikely to have cavity walls
  • Between 1932 and 1982 your house is likely to have cavity walls
  • Houses built after 1982 are likely to have cavity walls as standard

If in doubt, ask us or a builder to confirm your wall construction.

How Much?

A typical house will cost around £400 to insulate which will reduce your heating bills by as much as £130 per year, this equates to a payback of only 3 years, in other words, after 3 years you’ll have an extra £120 in your pocket, every year! You’ll also be helping the environment with a reduction in your CO2 emission of as much as 750kg per year.

  • Air Leakage

    There are several tried and tested high insulation options when building a new property.

    It is false economy to build to British Building Regulation standards. As a minimum you should consider Celotex’s 100mm fully filled cavity option but preferably you should go further and use either Xtratherm 150mm CavityTherm (see picture) or a fully filled 300mm cavity with Rockwool or Dritherm 37.

    The lower the wall U value the better the wall insulation. Set your target for new external cavity walls at 0.14 or less.

  • Air Leakage

    Install 120mm – 180mm Celotex or similar PIR foam-based insulation in new floors, or when replacing any existing, internal solid floors. Where the internal floors are suspended timber then the same material can be installed between the floor joists and any gaps filled with expanding foam. Do not be tempted to block up the air bricks or you will risk the floor timbers getting a wet rot infection.

    This type of insulation is robust and offers extremely good heat loss reduction and will greatly increase comfort levels within your home.

  • Top up existing or install all new glass fibre/Rockwool insulation, preferably within a plastic sleeve such as the Knauf Space Blanket to 300-400mm. Do not be tempted to take the cheap and easy route of installing under 300mm 400mm on flat ceilings in the loft.

    It costs very little and pays for itself in 1-2 years. In areas where a floor has been laid then lay the insulation on top of any floorboards to allow for future access and get the full benefit of the insulation. There are pre-insulated floor panels that can be bought from some builder’s merchants which are useful when a large area is required for storage. Do not compress the insulation as this will reduce it effectiveness.

  • On average, UK homes flush 25 – 27% of our fresh water supply down the toilet. This includes laundry, showering, car washing and garden watering. As we see the price of gas and other fossil fuels increase, the price of water is also increasing very rapidly. It makes perfect sense to have a rainwater recycling system installed both environmentally and for reasons of saving money.

    Installing is a simple operation when building a new property or refurbishing an existing property. It is relatively cheap to do for a builder/ground worker/plumber but it will require a new internal rainwater distribution pipe work system . It should pay for its self over 4-5 years by cutting water bills in half. Make sure you tell your water company as they will reduce your standing charges as well.

  • With new homes or when considering replacement windows, spend wisely. Triple glazing such as Ideal Combi, Velfac, Viking Windows or “The Green Building Store” range can now be supplied and fitted for roughly £450-500/m2. They will provide a long life (30 years+) solution with tremendous improvements in energy losses with U values of 0.8 to 1.0 W/m2K or less. Make sure you are being quoted whole window U values and not mid-pane values.

    If you have to fit double glazing, then make sure the completed windows come with whole window insulation values. The target should be no more than 1.6U. Be very careful you are not just quoted the glazing only figure which may sound good at 1.2U. Ask for warm edge spacers, argon filled 16mm cavity and Pilkington Optitherm soft low-E coating or similar.

    On buildings where the original single glazed windows must be retained due to listed building status, then secondary glazing can be used and we advise the use of double glazed secondary glazing to give significant improvements in heat loss. The same specification should be used as that suggested above for double glazing.

  • Air Leakage

    Minimum Specification – dryline on the internal face with 62mm laminate insulation board (50mm foil backed PIR or Celotex insulation with bonded on plasterboard), mechanically fixed to the wall then skim with plaster (3mm).

    Budget cost about £45/m2 of wall.

    Medium Specification – 92mm dry-lining installed as above.

    Super Insulation Specification – 162mm drylining.

    Note, depending on how flat the walls are and how damp, they may need to have treated timber batons with plastic spacers to give a level surface to fix the insulation panels to. It is also worth foam filling all joints and the top and bottom of the insulation panels to improve air tightness for all of the drylining solutions above.

    One way to approach internal wall insulation is to have it done on a room by room basis starting with the north facing, coldest rooms or the most frequently used rooms first. You can then do the rest as time, disturbance and budget allow.

SOLID WALLS (NO CAVITY) - External Insulation
  • Where it is possible to change the look of a building on the outside or where the property already has a rendered finish, then an external insulated render system (eg. K-Rend, Weatherby, Stow, Permarock or Weber) will provide the best possible reduction in heat loss. As this solution is only likely to be done once, it is well worth going for at least the minimum solution suggested below. Do not be tempted with a lower specification. The additional cost for the thicker solutions is minimal and the results well worth the small extra cost.

    Minimum Specification:
    100mm Polystyrene or Rockwool with reinforced self-coloured acrylic render finish.

    Medium Specification:
    100mm PIR high density foam/Celotex with reinforced self-coloured acrylic render finish. Target whole wall U-value 0.18 W/m2K.

    Super Insulation Specification:
    200mm Graphite polystyrene with reinforced self-coloured acrylic render finish. Target whole wall U value 0.13 W/m2K. External insulation has a dramatic effect on the heat loss of a building as it avoids most structural cold bridging effects and can greatly improve air leakage heat losses.

  • Conserving energy and controlling its use with thermal mass is one of the simplest and most rewarding energy conservation techniques you can use to improve comfort levels and reduce energy costs.

    By building it into new and existing homes you can provide a passive heat/energy store that will absorb excess heat during the day and release useful heat in the cooler evenings and night-time.

    Examples of thermally massive materials include hard dense surfaces such as tiles, stone floors, dense plastered/rendered walls, exposed brick work/stone work. Please speak to us to understand the full benefits for this passive system. It will never break down or wear out but will help to keep you cool in the summer and reduce the time through the year when you need to use your heating system.

  • Air Leakage

    UFH is a brilliant solution to include in new build and in homes undergoing extensive renovation to save energy and increase comfort levels. It also removes the need for radiators. Most plumbers will supply and fit it and it works best in new insulated solid floors but can also be used in some timber floor structures. Costs are very similar to radiator based systems and it comes with the added benefit of reducing running costs.

    It works extremely well with heat pump heating systems by allowing the heat pump to run at lower flow temperatures of 35-40 ° which is when they are most efficient. Speak to us about your home and we will talk you through the entire process of what to use, and where to use it.

  • Install heat recovery fans in the bathrooms and kitchen (approximately £350 each installed). Vent-Axia Low Carbon Heat Save is a good example: Consider the addition of a humidistat in the kitchen unit and a recirculation kitchen hood with carbon filter if you need a cooker hood.

    Mechanical Ventilation with Heat Recovery (or MVHR) is an essential part of Passivhaus low energy building design and in Low Energy Buildings.

    Carbon Legacy has developed specialist technical expertise in delivering MVHR systems for ultra low energy/ Passivhaus buildings. We offer a full design, installation & commissioning service to ensure the optimal efficiency and quietness with recovery rates of up to 95%. If you are building a new house or carrying out major renovation works then consider a whole house ventilation unit with heat recovery (WHVHR). An excellent manufacturer is National Ventilation who make various best in class units at reasonable cost. It is important to have an airtight structure to make this work.

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