Insulating pipework in unheated spaces does two things at once: it stops heat being delivered to a cold loft, and it substantially reduces the risk of freezing. Both are permanent, and the frost protection alone justifies it.
Two benefits, and the second is the big one
Heat that goes nowhere useful
A hot pipe running through a cold loft, an unheated garage or a suspended floor void is delivering heat to a space nobody occupies. That heat came from your boiler and you paid for it. On a long run – a farm, an older house with the cylinder a long way from the boiler, a converted property with awkward pipe routes – it adds up continuously.
Frost protection
This is the one that actually justifies the job. A frozen pipe in an unheated space splits, and the damage shows up on the thaw, frequently when nobody is home. The repair, the drying and the redecoration cost a multiple of what insulating the whole loft would have.
Thick loft insulation is excellent, and it means the loft is now considerably colder than it was when the pipes went in. A pipe run over the top of the insulation is sitting in outdoor temperatures. That is why frozen loft pipes are more common in well-insulated houses, not less.
Where it matters most
| Location | Why | Priority |
|---|---|---|
| Loft pipework above the insulation | Sitting in outdoor temperatures | Highest |
| Cold water storage tank | Freezes, and the ball valve freezes first | Highest – and do not insulate underneath it |
| Unheated garages and outbuildings | No heat at all | High |
| Pipes against uninsulated external walls | Solid walls in older property | High |
| External runs to outside taps | Outside by definition | High – and fit a drain point |
| Suspended floor voids | Ventilated, so effectively outdoor air | Moderate to high |
| Condensate pipes outside | Small bore, permanently wet – see frozen condensate pipes | High |
| Hot pipes in heated space | Heat loss goes into the house, so it is not wasted | Low |
| Primary flow and return in a plant room | Real heat loss on longer runs | Moderate |
The tank deserves a note: insulate the sides and the lid, and not underneath it. Heat rising from the house below is what keeps a loft tank above freezing, and insulating beneath it removes that.
Doing it properly
Insulation is easy to fit badly and the gaps are exactly where pipes freeze.
- Continuous. The gaps at bends, valves, tees and tank connections are where pipes actually freeze, and they are exactly where lagging is usually missing because it is fiddly.
- Correct bore. Lagging that is too large does not sit against the pipe and does very little.
- Adequate wall thickness for the location. Thicker in a loft than in a warm cupboard.
- Sealed joints, taped at butt joints and mitred properly at bends.
- Below the loft insulation where possible, so the pipe sits on the warm side of the thermal envelope. This is better than lagging a pipe that remains above it.
- Weatherproof grade outside, because ordinary foam degrades in sunlight and is largely useless after a couple of years.
- Not compressed, because compressed insulation is not insulating.
- Valves and fittings covered too, with purpose-made covers where available.
A lagged pipe in still cold air usually survives a normal cold snap. The same pipe with cold air moving over it frequently does not. Sealing the draught into a loft – at the eaves, around service penetrations, at the loft hatch – is often more effective than adding more lagging.
What we do alongside it
Insulation is rarely the whole answer to a pipe that has frozen. What goes with it:
- Re-routing where a pipe is in a genuinely hopeless position and can be moved to the warm side.
- Fitting isolation and drain points on external runs so they can be emptied in autumn – which is the only complete answer for an outside tap.
- Cold tank insulation and lidding, including the ball valve area.
- Cylinder insulation, where an older cylinder has a thin or missing jacket. That is continuous standing heat loss, every hour of every day.
- Draught sealing into the loft, which is frequently the actual cause.
- Trace heating, as a last resort where a pipe cannot be moved, insulated adequately or drained.
See frozen pipes for what to do if one has already frozen, and frozen pipes: thawing safely for the method.
Empty properties
Norfolk has a high proportion of second homes, holiday lets and rural properties that stand empty over winter, and they produce the most expensive water damage claims in the county.
Insulation is necessary and not sufficient for a property standing empty. The options:
- Heating on a frost setting, with somebody checking the property. Commonly a condition of the insurance – worth reading your policy.
- Water off at the stopcock, heating on frost setting. Better, though stored water in tanks and cylinders remains.
- Fully drained down, which means draining rather than switching off, and refilling needs care and re-dosing with inhibitor.
- Everything switched off and nothing drained. Do not. This is how empty properties are destroyed, and it is what we are called to every January.
Had a pipe freeze this winter? Autumn is when to insulate it, not the next cold snap.
Questions we get asked about this
Is pipe insulation worth it?
The heat saving is modest and permanent; the frost protection is what justifies it. One prevented burst pipe pays for insulating an entire loft many times over.
Should I insulate under the cold water tank?
No. Heat rising from the house below is what keeps the tank above freezing. Insulate the sides and the lid, not underneath.
My loft pipes are already lagged and one still froze.
Check for gaps at bends, valves and tees – that is where lagging is usually missing and where pipes freeze. Also look at draughts into the loft, which matter as much as temperature.
Should loft pipes be above or below the insulation?
Below where possible, so they sit on the warm side of the thermal envelope. That is better than lagging a pipe that remains above it in outdoor temperatures.
Does it help in summer?
Insulating hot pipes reduces heat loss year-round. Insulating cold pipes in warm spaces also reduces condensation on them, which is a minor but real benefit.
What about my hot water cylinder?
An older cylinder with a thin or missing jacket loses heat continuously, twenty-four hours a day, whether you use the water or not. It is one of the better-value things to improve.
What happens when you call
Call and describe it
You speak to an engineer, not a call centre. Most jobs can be narrowed down on the phone.
We look at it properly
A real diagnosis before a price, and a straight answer if it is not worth doing.
A written quote
Itemised, so you can see what you are paying for.
The job, and the paperwork
Certificates where the work needs them, and what will need attention next.
Where we do this work
Across Norwich and the whole of Norfolk. If you are on the edge of the county, call and ask — we will tell you honestly whether we are the right people.
- Norwich
- Wymondham
- Dereham
- Attleborough
- Aylsham
- North Walsham
- Cromer
- Diss
- Loddon
- Long Stratton
- Watton
- King's Lynn
Need this doing?
Call and describe the problem — you will speak to an engineer, not a call centre. Written quotes, no estimates over the phone.