The main reason to add insulation to a central heating system, is to provided the house with warmth and it will help to keep a comfortable temperature inside the house while using less energy. Insulating a central heating system is a very important factor in this, but equally is a well insulated home, including floor insulation, roof insulation and double glazed windows.

Thermal comfort

"Thermal comfort" is a measure of a person's satisfaction with his or her environment, and is achieved when a desirable heat balance, between the body and its surroundings are met.

These conditions include:

• Air temperature at feet level, no greater than 3C below that at head level.
• Airflow past the body is horizontal and at a velocity of between 0.2m and 0.25m per second. A variable air velocity is preferable to a constant one.
• Room surface temperatures not above the air temperatures.
• Relative humidity of between 40% to 60%.
• Air temperatures between 16-22C, dependant upon the activity being carried out, age a person and the amount and quality of clothing.

All of these factors are recognized to have an effect on a persons personal comfort and it is possible to implement a certain degree of control on all of these conditions, i.e. by installing insulating, reducing drafts, controlling condensation/ventilation and providing controlled central heating when needed.

Insulating performance

Installing insulation is one of the easiest and most cost effective methods of improving the energy efficiency of a home and is a good way to save a lot of money on your fuel bill, more than 50% of all heat produced can be lost through your walls, floor and attic spaces.

Insulation performance is measured by "R-value" — its ability to resist heat flow. Higher R-values mean a better insulation. Different R-values are recommended for walls, attics, basements and crawlspaces, depending on your area of the country. Insulation works best when air is not moving through or around it. So it is very important to seal air leaks before installing insulation to ensure that you get the best performance from the insulation.

Insulating the hot water pipes

A lot of heat is lost along the lengths of hot water pipes. The most important pipes to insulate are those running through the coldest places of your home, e.g. the attic. And those closest to the hot water cylinder, as these will be the hottest so will lose heat the quickest. If you have a boiler and a hot water tank, it is important to insulate the pipes between them. Next is insulating the pipes running from the cylinder to the hot water taps - where the first 3-4 feet or so is the most important section.

Roof insulation

In an average home, as much as 20% of the energy bill can be saved by installing insulation in the attic. A quick way to check if you have sufficient insulation is to look across your uncovered attic floor. If your insulation is level with or below the attic floor joists, you probably need to add more insulation. The recommended insulation level for most attics is R-38 (or about 12–15 inches, depending on the insulation type). In the coldest climates, insulating up to R-49 is recommended.

Floor insulation

In a regular household, as much as 10% of the heat can be lost through the floorboards. If there is easy access to the joists under your floorboards, you can insulate the floor from below by filling up all the spaces between the joists with mineral wool mat or expanded polystyrene boards.

Draft proofing

Common drafts are one of the main reasons why older homes feel cold and cost a lot to heat. Usually air leaks and drafts are easy to find because they are easy to feel — like those around windows and doors. But holes hidden in attics, basements, and crawlspaces are usually a bigger problem. Sealing these leaks with caulk, spray foam, or weather stripping will have a great impact on improving your comfort and reducing utility bills.

Double glazed windows

Regular draft-proofed, single glazed windows still allow a lot of heat to get lost (about 20% of the total heat lost from the house). Heat loss through windows can be halved by fitting double-glazing. Professionally fitted double-glazing can be expensive, but if you need new windows, having double-glazing fitted is the sensible thing to do as it makes rooms more comfortable and will save you money on the long run. Start by fitting double glazed windows into the rooms you use the most and on any of the larger windows first. Where double glazing can halve the heat loss through windows, double-glazing with low emissivity glass can reduce it by a further 30%.