Domakihub How to Insulate Hot Water Pipes and Cut Energy Bills
A simple DIY job that keeps water hotter, reduces wait times, and saves money every month.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
Uninsulated hot water pipes lose heat to the surrounding air every time you run the tap, meaning you wait longer for warm water and your boiler or heat pump works harder to compensate. The video above walks through the process visually, while this guide breaks it into clear, ordered steps suited to the pipe layouts common in Greek homes, holiday villas, and small hotels. Done in an afternoon, it is one of the highest-return DIY tasks you can tackle before summer or winter season begins.
Why pipe insulation matters in Greece
In Greece, water heaters — whether solar thermal, gas boiler, or heat pump — are often located on rooftops or in utility rooms far from bathrooms and kitchens. Long uninsulated runs mean significant heat loss before the water ever reaches the tap, especially overnight when ambient temperatures drop.
For holiday rentals and hotels, the problem compounds: guests complain about slow hot water, and back-to-back bookings leave no time to waste. Adding foam or fibreglass insulation to exposed pipes can raise delivered water temperature by 2–4 °C and meaningfully reduce energy consumption year-round.
Choosing the right insulation material
The most practical and widely available option for DIY use is pre-split polyethylene foam pipe sleeve (sometimes called armaflex or similar). It comes in standard diameters matching 15 mm, 22 mm, and 28 mm copper or plastic pipe, costs very little per metre, and requires no specialist tools. For pipes running very close to a gas boiler flue or other heat sources above 120 °C, mineral wool pipe sections with an aluminium foil jacket are the safer choice.
Self-adhesive foam tape can patch short gaps or joints, but full sleeves give far better coverage. For outdoor or exposed roof-terrace runs, choose UV-stabilised foam or apply an aluminium tape wrap over standard foam to protect against Greek summer UV, which degrades unprotected polyethylene quickly.
How to insulate your hot water pipes: 5 steps
- 1
Measure and buy the right sleeve diameter
Before buying materials, measure the outer diameter of your hot water pipes with a tape measure or calipers. In most Greek homes you will find 18 mm or 22 mm copper or cross-linked polyethylene (PEX) pipe. Match this to the sleeve's inner bore — a sleeve that is too loose will sag and leave air gaps. Buy enough length to cover every accessible hot water run from the boiler or solar storage tank to the first branch point, plus a roll of self-adhesive aluminium tape for joints.
- 2
Turn off the water supply and dry the pipes
Switch off the relevant supply valve and run a tap briefly to relieve pressure. Wipe each pipe section clean and dry with a cloth. Foam sleeves bond poorly to wet or oily pipe surfaces, and any moisture trapped under insulation on metal pipe can encourage corrosion over time. If pipes are dusty or coated with limescale residue, a quick wipe with a damp cloth followed by a dry one is sufficient.
- 3
Slide or slit the sleeve onto the pipe
Pre-split sleeves have a lengthwise slit that lets you press them onto an existing pipe without disconnecting fittings. Press the slit closed firmly along the full length. At elbows and T-junctions, cut the sleeve at a 45-degree angle with a sharp craft knife so the two cut ends meet neatly around the bend — a straight cut leaves a gap that acts as a thermal bridge. Work from the heat source outward so overlapping joints face away from the boiler.
- 4
Seal all joints and gaps with aluminium tape
Run a strip of self-adhesive aluminium tape over every lengthwise slit, every end-to-end joint between sleeve sections, and every mitre cut at bends. Press it down firmly so there are no air bubbles. This step is easy to skip but important: an unsealed slit can allow warm moist air to enter the sleeve, condensing on the cool surface and wetting the insulation from the inside. For outdoor runs, wrap the entire sleeve with aluminium tape for UV protection.
- 5
Restore water supply and check for leaks
Turn the water supply back on slowly and visually inspect every joint you disturbed. Run a hot tap and feel along the newly insulated pipe after two or three minutes — the outer surface of the sleeve should remain close to room temperature rather than warming up noticeably, confirming the insulation is doing its job. Label the insulated sections with a permanent marker noting the installation date; foam sleeves typically last 10–15 years before the foam compresses and loses effectiveness.
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FAQ
- Can I insulate pipes that run inside walls or under screed floors?
- Pipes embedded in walls or floors are effectively insulated by the surrounding masonry and are difficult to access without opening the structure. Focus on exposed runs — the stretch between your boiler or solar tank and the nearest distribution point, any pipes in unheated utility rooms or rooftop plant areas, and cold-roof spaces. These exposed sections account for the majority of standing heat loss.
- How thick should the foam sleeve be?
- For domestic hot water pipes, a wall thickness of 13 mm (half an inch) is the standard minimum and is sufficient for most interior runs in Greece. For pipes in unheated outdoor locations or roof terraces where summer and winter temperatures swing widely, opt for 19 mm or 25 mm wall thickness to prevent both heat loss in winter and heat pick-up from the hot ambient air in summer.
- Will insulating pipes help with Legionella risk?
- Insulation helps maintain water temperature above the 60 °C threshold that inhibits Legionella growth, which is relevant for holiday rentals and hotels that sit empty between seasons. However, insulation alone is not a substitute for proper system flushing and temperature management. If your property is unoccupied for more than two weeks, run all hot taps for several minutes upon return and verify your boiler thermostat is set to at least 60 °C.