Loft insulation regulations 2026: is it a legal requirement?
In England the law requires loft insulation when more than half of a roof is replaced and when a loft is converted. A let home also has to reach a minimum energy rating, which insulation counts towards. Otherwise no law requires it and no regulation says 270mm, but 270mm is what your energy certificate is marked against.
When is loft insulation a legal requirement?
The times the rules apply, and what each one asks for.
When more than half of a roof is renovated, the regulations say the whole roof has to be brought up to the current standard for heat loss, as far as that is feasible. In a loft that usually means a top up.
Turning a loft into a room needs building regulations approval, and the roof has to be insulated as part of it. Loft conversions.
No rule names loft insulation, but a let home has to be rated E or better, and insulation is one of the ways to get there.
No law makes you have it. The rules bite when work is done or a home is let, not on a house as it stands.
Do building regulations say I must have 270mm of loft insulation?
No. 270mm is a recommendation. The regulations guidance sets a figure for heat loss and gives 250mm as its example.
Three numbers get mixed up. The Energy Saving Trust recommends 270mm, and an energy certificate recommends 270mm wherever it records 150mm or less. The government's guidance to the regulations, Approved Document L, sets a target for how much heat a roof may lose. Its example for meeting that target when a roof is re-covered is a top up to at least 250mm.
The figure 270mm does not appear in that document, in the current edition or in the one that takes effect on 24 March 2027. So falling short of 270mm is not unlawful. It is common: 75.5% of lofts with a recorded depth in Cambridgeshire and Peterborough have less. How much loft insulation you need.
Sources: Approved Document L, Volume 1, 2021 edition with 2023 amendments; GOV.UK, Approved Document L, including the 2026 edition; BRE, RdSAP 10 specification; Energy Saving Trust, how to insulate a loft; our own count from government energy certificate data, explained on how we work out our figures. All read 10 October 2026.If the law does not make me, why insulate the loft?
Four reasons that apply to most homes, each one from a published source or our own figures.
- A quarter of the heat. The Energy Saving Trust says an uninsulated home loses around 25% of its heat through the roof.
- A better energy rating. In 2,149 homes here where the loft went from 100mm or less to 270mm or more between two certificates, and the walls, heating and windows were recorded the same, the rating rose by a typical 8 points. Homes where nothing changed rose by 2.
- Selling. You must have an energy certificate before you market a home, and a buyer sees it. 29,189 houses and bungalows here carry the line "Increase loft insulation to 270 mm" on theirs.
- Letting. The rating is what the law for landlords is built on, and the loft is one of the measures the government lists for raising it.
The rating figures compare certificates lodged for the same home between 2008 and September 2026. They are what happened in those homes, not a promise for yours. What your EPC says about your loft.
Sources: Energy Saving Trust, roof and loft insulation guide; GOV.UK, selling a home: energy performance certificates; GOV.UK, government response on privately rented homes; our own count from government energy certificate data, explained on how we work out our figures. All read 10 October 2026.Not sure what your loft has now?
The survey is free and you get a written price before any work starts.
Do I need approval to top up my loft insulation?
No. GOV.UK lists installing insulation in a roof space as work that does not need building regulations approval.
So there is no application to make and nothing to wait for. Replacing a roof covering is different. GOV.UK lists that as work that may need approval, unless the roofer is registered with a competent person scheme.
Sources: GOV.UK, when you do not need building regulations approval; GOV.UK, building regulations approval. All read 10 October 2026.What if my loft is already boarded?
The guidance allows for it. Where a roof is being re-covered and the boards are staying, it says the practicality of the insulation work has to be considered.
"Where the loft is already boarded and the boarding will not be removed as part of the work, the practicality of insulation works needs to be considered."
Approved Document L, Volume 1, Appendix C, Table C1.
That is not an exemption. The regulation itself asks for the upgrade as far as it is technically, functionally and economically feasible, and building control decides on a real job. Boards fixed straight onto the joists leave room for only as much insulation as the joists are deep. Boarding raised above full depth insulation avoids that.
Sources: Approved Document L, Volume 1; Building Regulations 2010, regulation 23. All read 10 October 2026.Does a landlord have to insulate the loft?
Not by name. Since 1 April 2020 a landlord cannot let a home rated below E unless an exemption is registered.
How the home reaches the rating is up to the landlord, and the certificate's own recommendations are the place to start. In January 2026 the government published a decision to raise the standard to C, with a single date of 1 October 2030, and said new legislation was needed first. GOV.UK has the decision and any later change.
Sources: GOV.UK, landlord guidance on the minimum energy efficiency standard; GOV.UK, improving the energy performance of privately rented homes. All read 10 October 2026.Short answers
Do I need loft insulation to sell my house?
No. GOV.UK says you must order an energy certificate before you market the home, and it is valid for 10 years. There is no minimum rating for a sale. The buyer sees what the certificate says about the loft.
What are the loft insulation regulations for 2026?
In England in 2026 the rules are in Approved Document L. A roof has to meet a heat loss figure when it is renovated or a loft is converted, and the usual way is at least 250mm of insulation. A new edition takes effect on 24 March 2027 and, like this one, does not name 270mm. GOV.UK has both editions.
What happens if you have no loft insulation?
Nothing in law, for a home you live in. The Energy Saving Trust says an uninsulated home loses around 25% of its heat through the roof, and your energy certificate will recommend 270mm.
Is the government giving out free loft insulation?
There is a grant for some lower income households, and you apply for it yourself. Loft insulation grants in Cambridgeshire has who qualifies.
Do new builds have to have a set depth of loft insulation?
No. A new home has to meet a heat loss target, not a depth. Of homes built here since 2012 with a depth on their certificate, the typical figure is 300mm.
Who do I ask about building regulations in Cambridgeshire?
Your council building control team. 3C Building Control covers Cambridge, South Cambridgeshire and Huntingdonshire. East Cambridgeshire has its own team, CNC Building Control covers Fenland, and Peterborough gives advice on 01733 453422.
This page covers England and is general information, not legal advice. For a particular job, ask building control.
Sources: GOV.UK, energy performance certificates; GOV.UK, Approved Document L; our own count from government energy certificate data, explained on how we work out our figures. All read 10 October 2026.Find out what your loft has
Required or not, it starts with knowing what is up there. Our survey is free and takes about twenty minutes.
Written by Ben Criddle, who runs Complete Loft Services. Published . Facts checked on .