My house is freezing, I like it that way as it saves the Dolphins. I work during the day in a glorified outhouse that equalises with the outdoor temperature every evening. I wouldn’t survive the winter without the combo move of Icebreaker Merino 260 baselayer, and the warmest Fleece I can find which is Patagonia Better Sweater for normal fit or the classic Synchilla for slightly bulkier but warmer still – not found other fleeces that comes close. Last ages too.

I’ve got a Regatta zip up fleece which I find is marginally warmer than my Berghaus ones.

Old school fibre pile fleece jackets are just about the warmest things going. Lots of places do them but I’ve got an anchient Rab one. Another good point with them is they don’t lose loft like down and synthetic insulation will when sitting around in it.

Mountain Equipment ‘Moreno’ jacket, Patagonia ‘Retro Pile’ jacket, Helly Double Pile Jacket etc.

Although, remember clothing doesn’t generate heat – they just keep what your body generates in close to you. Doing some star jumps or similar, drinking hot drinks, being well fed etc are all very useful.

No heating for the time being, I’m wearing a Jottnar Yak wool base layer with an old fleece hoodie I bought from a surf/skate shop in Bristol. It’s big and baggie, made from that rough fleece, called Berber, I think. My favourite cool/cold weather item, but I can’t find the maker online; it’s a Low Pressure Stormrider, and I think there was a surf shop of that name in London.
Shame, I’d buy a couple more if I could find them.
Anyway, a couple of different layers, maybe wool base with fleece over the top, and sone fleece or wool fingerless gloves to keep the extremities warm as well, as nobody’s mentioned the hands.
Something like this one: https://www.alpinetrek.co.uk/columbia-rugged-ridge-ii-sherpa-pullover-hoodie-fleece-jumper/

is he cold, or are his extremities cold? If the latter, putting layers on his core may actually make the problem worse, as flow to the extremities (which are now more exposed, compared to his core) won’t improve at all.