These reverse a previous rule that obliged many homeowners to undertake more than one energy efficiency improvement at a time, such as putting in new windows, changing heating systems and insulating ceilings.
Experts had said this was the most efficient way of boosting the energy rating of properties.
However, builders say the extra expense of doing all the work at once discouraged homeowners, and they saw orders drop sharply.
Many builders are looking for work after a post-Covid boom in renovation has begun to slow down. At the same time, demand for new homes has fallen due to high interest rates and inflation.
The latest changes, which for the time-being have been announced as only being until the end of this year, include:
Owners of homes with the lowest, F or G, ratings were set to be excluded from doing one-off works, and obliged to carry out major renovations boosting the property by at least two letter categories. This will now no longer be the case.
A rule that you could not apply for a grant just for insulation work, but had to combine this with changing your heating or hot water system to a more eco-friendly version no longer applies.
However, one aspect has been tightened: you can no longer apply for a grant for a double-flow ventilation system, unless you also apply to do insulation work.
Effy, an online company that specialises in energy renovation estimates, has pointed to an immediate rise in insulation work as a result.