Insulation and building fabric in a commercial EPC upgrade

Why it scores better than it pays

A non-domestic EPC is an asset rating of the building and its services, not of your metered use, and fabric is a large part of what that model looks at. Improve it and the rating moves meaningfully. The problem is simply that the capital involved is high and the energy saved per pound spent is lower than almost anything else available.

That gap between what it does to the certificate and what it does to the payback is why fabric usually belongs to a refurbishment rather than to an energy project. When the scaffold is already up and the roof is already coming off, the marginal cost collapses and the decision reverses.

The cheap end people skip

Not all fabric work is a re-clad. Several of the cheapest measures in any building are fabric measures that nobody thinks of as fabric.

• Loft and roof void insulation where there is a void to get into, which is ordinary materials and labour and nothing else.
• Draught-proofing around doors, loading bays, service penetrations and roller shutters, which on an industrial unit can be a very large uncontrolled air path.
• Insulating the perimeter of a heated space that abuts an unheated one, which is common where buildings have been subdivided.
• Fast-acting or air-curtain protection at doors that stand open through a working day.

On an industrial building, the gap under a roller shutter is frequently worth more than any amount of wall insulation, and costs a fraction of it.

When fabric is unavoidable

If you are several bands below where you need to be, and the lighting and the plant are already good, fabric is what is left. That is the honest answer, and it is usually also the point at which the conversation becomes a refurbishment conversation rather than an energy one.

It is also unavoidable where a building is physically uncomfortable. No amount of efficient heating fixes a building that cannot hold the heat.

The trap: doing it in the wrong order

Improving fabric changes the heat demand of the building, which changes the correct size of the heating plant. Replace the boiler first and then insulate, and you own a boiler sized for a building that no longer exists, running inefficiently at part load for the next fifteen years.

If both are on the list, fabric is specified first even if it is installed second.