Architectural design specialists - Home extension plans

Energy efficiency home make over - August 2012

There is an enormous amount of housing in the UK that is not considered energy efficient but is however in an area that you may prefer to live, invest in or is a house of particular design merit that would be uneconomical to recreate. Much emphasis is placed on sustainable new developments but far too little regard is given to reviving and upgrading the existing housing stock.

As part of a house renovation and or extension/conversion project the whole house can be reviewed and designed to be highly efficient reducing your yearly expenditure in the long term and significantly improving the energy rating of the house for sale or rental purposes.

There are several areas that need to be addressed, you may wish to do some of these to get some benefit, or a whole house energy efficiency make over to get the maximum benefit.



You spend a lot of money heating your house. Many older style homes are not adequately insulated therefore much of the heat you pay to produce escapes and precious natural resources are also wasted. To remedy this the structure of the house needs to be identified. Does house have a more modern cavity wall construction or an older style solid wall construction, does it have a suspended floor or a solid floor, pitched roof or a flat roof.

Cavity wall construction - The cheapest and easiest method of upgrading your home is to employ the services of a cavity wall insulation company and to take advantage of any grants available.

Solid wall construction - Upgrading this type of construction is more expensive however done right it will provide a more efficient home than a more recent cavity walled house. Insulating the walls from the inside is the least expensive option, this does have its draw backs however. You are going to loose internal space from the rooms and the walls will need to be refitted with skirting boards, architraves, window reveals and sill boards, power sockets etc. The room will also of course require redecoration and the solid part of the wall is outside the thermal envelope meaning you can't take advantage of the thermal mass storing your heat therefore the house will cool down faster. The benefits however is that the room will heat up faster if you don't spend long periods of time within the rooms affected and the external appearance of the building will remain as existing.

If however you are planning extensive external works such as an extension you could consider external insulation. The benefit being you can take advantage of having the thermal mass within the envelope of the insulation and you don't loose space out of the rooms. The down side is that the external appearance will have to change to some extent either by having to render the building or apply brick slips. This option is not suited to areas affected by a conservation area or listed buildings. If you have the solid walls within the thermal envelope then your house will take longer to heat, but it will retain the heat for a longer period of time. Great if you spend more time in the rooms affected.


The loft - Upgrading the loft space can be as simple as laying out rolls of mineral wool insulation or can be highly involved. If you never plan to utilise your loft space then mineral wool insulation is the cheapest and simplest way to insulate. Go for as much loft rolls as you can get in, Its cheap. However mineral wool insulation does come with its own hazards so you may wish to pay for an insulation company to do the work. The down side to mineral wool insulation is that it can't be compressed, when compressed it doesn't work efficiently so therefore you can place items on it.

Another solution if you plan to convert your loft or use your loft for storage is to insulate between and below the rafters with a rigid insulation. Two brands of PIR rigid insulation come to mind Celotex and Kingspan however there are others that are of a very similar specification. Technical guidance should be sought from the manufactures and you need to ensure that the timbers can ventilate by allowing a 50mm air gap over the insulation placed between the rafters. The advantages of this is that the space within the loft remains open and providing the structure has been upgraded the loft can be converted for use as a room or storage also if installed correctly the loft insulation will help control air leakage and therefore heat pouring out of the roof via drafts. The disadvantage is that installing insulation within the rafters is quite laborious and the material cost is more expensive. Loft conversions although in relative building costs are inexpensive can be quite complex and there are building regulations to comply with so it is suggested that expert design and construction advice is sought before attempting a conversion.

If you have an older property, some of which do not have a roof felt installed and generally the roof is in good order you might consider having a spray applied foam insulation installed. This does need to be done by a trained installer with the correct equipment to get a decent job, however the advantages are that the roof space is sealed air tight and entirely encapsulating the timber rafters and battens ensuring no water gets to them causing rot. The spray foam insulation also helps to bond the underside of the tiles or slates which will further extend the life of the roof. The disadvantage of this type of insulation is that once it has been applied doing further modifications can be difficult and the application of the insulation can be very messy.

Flat roofs offer few upgrade options as they are noramally associated with low ceilings and thin structures. You can however make some improvements by stripping the ceiling and installing a rigid insulation tightly between the joists. Like a loft conversion the timbers need to be ventilated and the ventilation must be continuous to each end of the rafters. To complete the insulation detail you ideally would want to insulation below or about the joists. The advantage of insulating below the joists is that you don't have to affect the roof finish. The advantage of insulating above the roof is that you don't have to affect the ceiling height, but you do have to redesign the roof finish and weathering. In some cases the raising of a roof may require planning approval so it's best to check with your local planning office before commencing any work.


The floor - Upgrading the floor will depend on the type of construction. A solid floor found on most newer styles of construction do not cost effectively lend themselves to thermal upgrading. You can however lay insulation boards under engineered timber or laminate flooring and you can use a decent underlay under carpet.

A raised timber ground floor offers more scope than a solid floor in that the timber floor will normally have a void below that can be used for insulation. If you want to keep your existing floor boards and you have an accessible crawl space under the floor then you can install rigid insulation between the floor joists. This is a relatively low cost method of insulating the floor however you do need to work in confined spaces and you have to work around services that could be hanging from the floor joists. When installing insulation in this way you also have to ensure that you do not block off the sub floor vents and this will likely result in the eventual rotting of the timber floor structure. (Never block off sub floor vents to a raised floor)

Should you not be precious about an existing timber floor you could totally remove the floor boards and joists being carefull to ensure that you don't undermine walls without providing new support. Pour a new concrete base over a continuous polythene damp proof membrane on blinded compacted hardcore. Lay a suitable rigid floor insulation over the concrete, a further polythene layer then pour a screed. Advantages of this method when done correctly is that you will have a solid, level and well insulated floor with plenty of thermal mass. You can also lay under floor heating pipes within the screed. The disadvantages of this method is that it is quite labour intensive and can be expensive. With this system in most cases sub floor vents become redundant.


Windows/doors - This is an easy upgrade although not always cheap. Replacing old windows and doors with modern double glazed units will be highly benificial. There are very high grades of glazing on the market, the better the glazing the more you pay. Modern windows or doors needn't be common UPVC framed although they are the cheapest option. There are several manufacturers that offer thinner frames and of different materials such as timber and aluminium. Tasks to consider after replacing windows or doors is that you will be likely have to make good the window reveals and sill boards. Careless workmanship may result in unsightly lines of sealant from the previous windows being visible. Before investing in replacement windows check that you are not in a conservation area or that the building you are upgrading isn't listed. There may be special permissions required to change windows, even if the new windows are of a similar style to the windows being replaced.



Heating systems - Your heating appliance will have a large impact on the running costs of your home. Old gas or oil fired boilers without a built in flue heat recovery system will be less efficient than modern condensing boilers. However these aren't your only options. You may have a solid fuel boiler such as coal fired or wood burning. All fossil fuel boilers have high running costs and as the costs of the fuel increases these running costs will also increase. Other types of heating systems to consider are wood chip or pellet boilers, these are green and effective however you still have to purchase and store the fuel. Heat pumps are very efficient and have a relatively low running cost, they don't require fuel deliverys and don't directly burn fossil fuels. However the installation costs can be high and in the case of ground source heat pumps you either need alot of land or pay the premium of having bore holes for the installation of the ground collectors. Air source heat pumps are ideal when you don't have the space or budget for a ground source heat pump, they are not as efficient as a ground source heat pump they are however more efficient than a gas or oil boiler.
Any wet heating system you choose to install will benefit from having a solar hot water panel providing you can install a panel on the ideal roof orientation.
Direct electric heating is the least efficient requiring large amounts of energy to produce the heat required. The advantage of direct electric heating is the installation costs and it homes where it is impractical to install a wet system. If you choose to go down this route then it will pay to look for the most efficient systems.

Radiators or under floor heating - Radiators are cheap, react fast to input and can come in a variety of styles however their description is a little misleading. Radiators warm the air within the fins, convection then causes the air to rise to the ceiling which cools and falls, cooled air is drawn back into the fins to be warmed up and the process repeats. The down side of this is that radiators can cause what feels like a draft and alot of heat is required to make them operate correctly. The radiator fins need to be cleared of dust regularly to ensure that they work at their best.
Under floor heating systems come in two main types, a wet system heated by a boiler and electric. Under floor heating has a higher initial install cost however when correctly designed and installed they heat the room evenly. The floor feels warm and there is no apparent draft generated. Underfloor heating systems run at a lower temperature so therefore the heating system doesn't need to use as much energy to warm your home when compared to radiators. Apart from the inital cost of installation, the down side of under floor heating is that it has a slower reaction time so it is less suited to rooms that are used intermittently when compared to radiators.
If you are using radiators you should install individual room stats to control the temperature of each radiator. Wet under floor heating needs to be controlled at a manifold which is controlled by room stats. Electric underfloor heating will also need to be controlled by individual room stats. The main reason for this is to ensure that the heating system isn't putting energy into a system that doesn't require it thereby saving energy and your running costs.


Lighting - One of the simplest upgrades you can do to your home is change the light bulbs to compact flourescent units. The down side of compact flourescent bulbs is that they can't be dimmed, have a warm up time to reach full brightness and are not generally suited to passive infrared detectors. A less efficient alternative are mains voltage halogen bulbs. You can consider changing to LED lighting however this tends to be low voltage requiring a transformer and so requires more extensive electrical wiring. The same can be said for low voltage halogen bulbs which also requires a transformer.

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