Insulation in a commercial building
Insulation is a fabric decision. It rarely pays back quickly alone. It makes everything fitted afterwards cheaper to run.
What it actually is
Insulation reduces the heat a building loses, so the heating system has less to do. In a large single storey building, most of it goes through the roof.
The strongest cases are a reroof, a heating replacement, or a rating problem.
Insulation reduces the heat a building loses, so the heating system has less work to do. In a large single storey building the roof is the dominant loss, which is why roof and loft work is usually the first thing looked at on industrial and retail stock.
It is a fabric decision rather than a plant decision, and it behaves differently from everything else on this list. It rarely pays back quickly on its own, but it makes every heating measure fitted afterwards smaller, cheaper and cheaper to run. It also lasts as long as the building does and needs no maintenance.
The three moments when the case is strong are a reroof, a heating replacement and a rating problem. In the first, the access is already paid for. In the second, better fabric shrinks the plant you are about to buy. In the third, fabric is modelled directly into a non domestic assessment.
There is also a comfort and productivity argument that does not appear on a bill. An uninsulated shed is cold in February and unbearable in July, and both affect the people working in it.
Which buildings it suits, and which it does not
It suits older stock and buildings with high heating demand. Fabric first makes a heat pump smaller and cheaper to run.
It suits you less where the building is barely heated, or where a lease makes fabric work impractical.
- Older heated warehouses and industrial unitsGood fitLarge roof area, high losses, and often very little insulation in the original build.
- Buildings due a reroofGood fitThe best moment there is. Access and stripping costs are already being paid.
- Buildings about to change heating plantGood fitDo the fabric first and buy a smaller heat pump or boiler that runs cooler and cheaper for its whole life.
- Older offices with poor fabricDependsRoof and floor work is straightforward. Walls and glazing are far more intrusive and usually wait for a refurbishment.
- Buildings sitting at a poor EPC bandDependsFabric is modelled directly, so it moves a rating. Compare it against lighting, which is often cheaper for the same movement.
- Unheated storageRarelyThere is little heat to keep in. Save the money for a measure that acts on the electricity bill.
- Listed and heritage buildingsRarelyNot impossible, but consents, breathability and moisture risk make it a specialist project rather than a routine one.
- Short remaining lease with no recovery routeRarelyA long life asset paid for by whoever has the least time left in the building is the wrong way round.
What it typically costs and saves
- Installed cost
- An installer prices this one
What drives the variation
- •Which element is being insulated. Roofs are usually the cheapest per square metre, walls and floors far more.
- •Whether the work is internal or external, and whether the building stays in use during it.
- •Access, scaffolding and any temporary weather protection.
- •The material and the thickness required to meet the target performance.
- •Any remedial work found once a construction is opened up.
- •Fire rating and insurer requirements, which can dictate a more expensive material.
How this appears on your building
- Fabric detail has not been surveyed, so no saving has been produced.
What decides whether it works on your building
What is there now
The EPC and the original construction give a strong indication, and an inspection or a thermal survey confirms it. Buildings from before modern building regulations are usually the ones worth doing.
Whether other work opens the fabric anyway
A reroof, a refurbishment or a change of use turns an expensive job into a marginal one, because the access is already there.
Heated area and how the space is used
A building heated to a comfortable working temperature all winter gains far more than one heated to keep frost off.
Condensation and ventilation risk
Changing where the dew point sits in a construction can cause damp and corrosion if it is done without thought. This is the main technical risk in fabric work and it deserves a proper design.
Tenure
Fabric is a landlord matter in most commercial leases. If you occupy under a lease, you will usually need consent, and you should look at whether the cost can be shared.
Fire performance
Insulation materials have fire ratings, and insurers as well as building control take an interest. Confirm the specification with your insurer before work starts.
How long it takes and what it disrupts
Survey and design
Establish the existing construction, the target performance and the condensation risk. On anything other than a simple loft this is a design exercise, not a product choice.
Roof work
Weather dependent and noisy. It can usually be phased in bays so the building keeps operating underneath, with protection below.
Internal wall or floor work
The most disruptive version, because it takes the space out of use. This is why it usually waits for a refurbishment or a void period.
Afterwards
Heating controls should be reset for the new fabric. A building that needs less heat but is still run on the old settings gives back much of the gain.
What usually goes wrong or gets missed
Done alone when a reroof was coming
The access is the expensive part. Paying for it twice is the most common avoidable cost in fabric work.
Heating replaced first and sized to the uninsulated building
You then own oversized plant for the next twenty years and it runs inefficiently every year.
Condensation risk not assessed
Interstitial condensation causes damp, mould and corrosion in steel framed buildings, and it appears long after the installer has gone.
Thermal bridging ignored
Insulating the field of a roof and leaving every junction untreated delivers much less than the calculation promised.
Ventilation reduced along with the heat loss
A tighter building needs a deliberate ventilation strategy, particularly where there are people or processes producing moisture.
Insurer not consulted on materials
Discovered at renewal, this is an expensive surprise.
- •It is done alone, when a reroof would have paid for the access.
- •The heating system is replaced first and sized to the uninsulated building.
- •Ventilation and condensation risk are not considered.
What to ask an installer
- 01What is the existing construction, and how did you establish it?
- 02What performance will this achieve, and what performance does the building have now?
- 03Have you assessed condensation risk in the new build up, and can I see that?
- 04How are junctions and thermal bridges treated?
- 05What is the fire rating of the material, and has my insurer confirmed it is acceptable?
- 06Can the building stay in use, and how do you protect the space below?
- 07Is there any work planned to this roof or elevation in the next few years that this should be combined with?
- 08What will this do to my EPC rating, and have you modelled it or estimated it?
- 09Does the price include access, weather protection and making good?
- 10Should the heating controls be reset afterwards, and is that included?
How it interacts with other measures
With a heat pump
The pairing that matters most. Better fabric lets the building run at a lower flow temperature, which is exactly what makes a heat pump efficient, and it lets you buy a smaller unit.
With a boiler replacement
Same principle. Insulate first and size the plant to the improved building, not the old one.
With solar
Little direct interaction, since insulation acts on heat and solar on electricity. The exception is a reroof, where doing solar, roof and insulation as one project saves a full set of access costs.
With an EPC rating
Fabric is a direct input to a non domestic assessment, so insulation moves a rating. On a building that is already close to a band boundary it can be decisive.
Does it move an EPC rating
Fabric is a direct input to a non domestic EPC, so insulation can move a rating.
Ratings matter most if you let the building. Our guide to MEES and the commercial EPC standard sets out the thresholds, the dates and what to do if a building falls short.
Common questions
Does commercial insulation pay for itself?
Rarely on its own and rarely quickly. It pays when it is combined with work that was happening anyway, such as a reroof or a heating replacement, or when a rating has to move. Its lasting value is that it reduces the size and the running cost of every heating measure that comes after it.
Where should I insulate first in a commercial building?
In a large single storey building the roof, because that is where most of the heat goes and it is usually the cheapest element to treat per square metre.
Will insulation improve my EPC rating?
Yes, fabric is modelled directly in a non domestic assessment. Whether it is the cheapest way to move your particular band depends on the building, and lighting is often cheaper.
Can insulation cause damp?
It can if the build up is not designed properly, because insulation changes where condensation forms within a construction. This is the main technical risk and it is why the design matters more than the product.
Can I insulate a building I lease?
Usually only with the landlord's consent, since fabric is a landlord matter in most commercial leases. If the remaining term is short, look at whether the cost can be shared before committing.
Related reading
Where these figures come from
Show the provenance
- Installed cost: An installer prices this one
- The existing fabric, access and specification have to be assessed first.
The figures on this page are modelled ranges for UK commercial buildings, not a quote for yours. Add your building and we will model it on your own roof, load and rating.