I want to insulate my hot water pipes.

[Fluffycloudland77]

Is the cheap grey foam as good as the thicker or should I spend the extra?

The thicker grade is required in unheated spaces such as outdoors, lofts, garages, under ground floor.

It is better, so if you have room for it around the boiler and cylinder, use it where it will fit.

You can cut or trim it with a serrated knife.

Thank you, I suspected the thicker grade would be more effective.

One of the pipes is too close to the door frame for insulating, should I wrap silver insulation "bandage" around it?

Like this

I'd go for as thick as will fit. This is one of those simple insulation measures (along with insulating a hot water cylinder) that will pay for itself in less than a year.

I'm struggling to picture the pipe and the door frame... If it's a short length, I'd do whatever is simplest, but if its a decent run, I'd probably wedge a bit of flat insulation between the pipe and the surface, then cut the pipe insulation in half along its length and stick that down over the top. Does that make sense?

There's literally 1.5cm gap between door frame & pipe, plus it's a 22mm pipe that's pumping the heat out.

And you definitely can't get any of this stuff round it? www.diy.com/search/insulation%20foam/Climaflex-Pipe-Insulation-22mm-x-13mm-x-1m-9273771

Too thick...it's a tight gap

you may have to cut a "flat" as a chord across the diameter of the insulation to make it fit against the wall. otherwise, the internal grade will be better than nothing. pipe clips usually hold the pipes between 10 and 15mm off the wall, though you can get special longer, adjustable ones. You can notch the insulation to fit it round the clips. external walls are much colder than internal walls.

Insulation effectivness is mostly proportional to its thickness, plus the material of which it is made. the stiff plastic foam is fairly resistant to damage.

Just measured gap, 5mm at most, I will try and wrap what I can and duct tape it.

Fun.

if you buy some of the tubular pipe insulation, and look at the end of it, you will see it has a partly-cut slit in it.

Using a bread-knife, or similar, cut a flat edge off the insulation, cutting off the side with the slit in it

Like the line marked "Y" in this picture.

The amount you cut off,marked "X" will be the thickness of the insulation (probably about 10-12mm) less your gap of 6mm, so about 4-5mm.

You can then push the slit over the pipe, and it will clip on with its natural springiness, and look quite neat, even though there is only 6mm thickness between the pipe and the cut edge at the narrowest part. It will compress a bit if your cutting is not very accurate. You can notch out for any pipe clips. You might find it easier to cut the insulation into shorter lengths and trim them individually. It is quite easy to cut, I bet you'll find you can do it.