Jeff Howell: do I have to contribute towards maintenance costs? This is one of the problems with the "Right to Buy" scheme. Private leaseholders are obliged to pay their share of the maintenance costs, and this will be made clear in your lease. The only argument your solicitors might have will be the cost of the contract. But housing associations and local authorities are bureaucratic bodies with many departments and officials employed in them, and are not known for getting value for money for building maintenance works. Chp for free? Q: My power company, Flow Energy, is to bring out a new boiler next year which generates electricity as it uses gas to heat the home. It is inviting customers to sign up for a free boiler and free installation costs. After five years, the customer gets the feed-in tariff as well. What is your opinion of this new boiler? AW, by email A: There is nothing "new" about combined heat and power (CHP) boilers. The concept of CHP has been around for more than 130 years. The principle is sound enough - every home needs electricity, so why not generate your own, using gas to drive a micro generator? And then, because the generator produces waste heat, why not use this to heat your radiators? On a large scale, this would be a great idea. There are many communal district heating schemes around Europe, the most famous being the one in Odense in Denmark, where waste heat from the power station heats thousands of homes at very low cost. But as for an individual house having its own micro CHP boiler, I suggest you ask yourself why it's never caught on before, and why this company is now trying to get you to sign up for one. Maybe it's because the system will only be economically viable with a taxpayer-funded feed-in tariff (FIT) payout of around 12p per unit, which the company will keep for itself for five years. After that you might find you inherit a micro CHP boiler in need of expensive care and maintenance. Water nuisance Q: Our house is heated by a combi boiler, which also heats the water. We have always had problems in the sudden variation in water temperature when using the shower, especially when water (hot or cold) is being drawn elsewhere in the house. Is there some sort of balancing/equalising item of equipment that could eliminate the problem? Access to both feed pipes is by way of an inspection panel at the rear of a built-in wardrobe, with the shower unit housed the other side of the stud wall. There is ample room for any additional equipment. JB, Calne, Wiltshire A: Combi systems heat mains water "on demand" as it flows through the boiler. This means that both the hot and cold water are flowing at mains pressure, supplied by a single incoming mains pipe. If you open the hot tap on your shower, less water will flow through the cold tap, and vice versa. It is almost impossible to manually adjust a shower running from a combi system. Fortunately, the "additional equipment" you need is readily available, and is called a thermostatic shower mixer. Some makes are housed in the wall behind the tiling, and this might be a neat solution in your case, as you have a rear access panel. Otherwise I prefer the thermostatic "bar mixer" type, where everything is surface-mounted, so that should the thermostat need attention, it doesn't require removal of the tiles.