THE STANDARD ASSESSMENT PROCEDURE (SAP)
The conventional gas-fed boiler still functions as the primary heat source in most UK homes. This familiar, user-friendly appliance works with both radiator and underfloor heating systems, and it can be paired with intelligent controls to help maximise the overall efficiency of your heating setup. Deciding on the right model for your property comes down to the size of the house, how many people are living there and the thermal efficiency of the building fabric.
The SAP test is the means the government uses to determine the future energy performance of your new home. It’s a necessary step for self builders, as it shows whether your new house will comply with the energy and carbon requirements laid out by Building Regulations.
The main options for these appliances boil down to three types: regular, system and combi. Each differs in how they provide domestic hot water for taps, showers etc. “A regular boiler takes cold water supply from your mains supply and stores it in a tank, ready to be heated,” says Mark Wilkins, technologies and training director at Vaillant. “Cold water is then fed into the cylinder, where your boiler heats it and stores it until it’s needed.” Able to supply multiple outlets at once, regular boilers were once the go-to option for bigger family homes – but they need more space, requiring an expansion vessel in the loft.