The full list of improvements covered by the scheme has been split into "primary" and "secondary" categories.
This is important, because the homeowner will only qualify for a voucher if they are installing at least one of the improvements on the primary list.
Insulation: including solid wall, cavity wall, under-floor, loft, flat roof, room in roof and park home insulation.
Low carbon heating: including air source heat pumps, ground source heat pumps, hybrid heat pumps, solar thermal systems and biomass pellets boilers. (They'll need to have sufficient wall insulation to qualify for low carbon heating).
If they already have at least one of these measures installed, they can apply for a voucher to install "top-ups" (for instance, to install additional materials to reach a required level), but not for replacements.
Homeowners can apply for both a primary improvement and a top-up from the primary list, however, they should remember that top-ups cannot exceed the value of their primary improvement.
This means if they received £1,000 toward installing insulation as a primary measure, they could then only get a maximum of £1,000 to put toward your chosen top-up.
If they are installing at least one primary improvement, they can also use some of the money leftover in your voucher to install "secondary" improvements too.
Secondary improvements: Draught proofing
Windows and doors: replacing single glazing with double or triple glazing, installing secondary glazing in addition to single glazing, upgrading to energy efficient doors.
Heating controls and insulation: installing appliance thermostats, hot water tank thermostats, hot water tank insulation, smart heating controls, zone controls, delayed start thermostats or thermostatic radiator valves.
Bearing in mind that the subsidy received for the secondary measure can only be equal to the subsidy for the primary measure.
So, if a homeowner receives £1,000 to help pay for their primary measure, they could only receive up to £1,000 for the secondary measure too – even if it ends up being more expensive.