How do I warm up my kitchen?

Sounds like you need some new insulation. Is your kitchen over a basement or a crawl space? Do you have any heat in your kitchen? Can you add heat tape to your pipes so they don't freeze?

Sounds like you really need better insulation, particularly where your pipes run back behind the sink in the kitchen.

Sounds like u need insulation put in..also wrap the pipes with insulation around them

One thing you could do is remove the wall board under the sink to expose the pipes. That way the inside house heat can keep them from freezing and if there is outside air coming in you will be able to feel it right away and possible determine where it is coming from.

Sorry, but this sounds like a botched home renovation. Pipes should not freeze! Did they follow building code??? Bet they didn't. We're inspections performed? Permits pulled? Bet not! I would call them back (even after 4 years) and get them to remedy.

Or hire a new licensed contractor to come in and evaluate the situation and fix it. The kitchen should be toasty warm. Is there a heating duct to the kitchen? If so, and you are not getting heat, call out a licensed HVAC service.

Makes me wonder what other corners they cut . . .

https://www.consumer.ftc.gov/articles/0242-hiring-contractor

So sorry this happened to you, now you know better. If it were me I certainly would not have accepted such sloppy work or even paid them.

Simplest stuff first - make sure you haven't blocked or closed off any heating vents or boiler pipes. Contractors sometimes close vents off during renovation to reduce the amount of dust that gets into them or pipes to boilers to avoid burns and leaks. Also, have your heating system checked by a professional to make sure it is working correctly.

Assuming that your heating system IS working correctly and that the kitchen is just cold, adding insulation is the best long term solution, but is costly. It can be blown in from the outside without disturbing tour renovations, but needs to be done by a professional. If you have insulation and it just isn't working well, open up the wall near the pipes to see if there's a leak that has gotten the insulation wet. Wet insulation is not effective.

Until you are able to afford to fix the insulation issue, leave the pipes exposed as much as possible under the sink by removing cabinet doors so what heat there is can get to them.

Hang quilts or pretty but thick fabric on walls where you are able to act as temporary insulation (that's what tapestries in ancient castles were for).

Use a small fan attached to the doorframe of the kitchen or near the doorway to help circulate warm air from the rest of the house into that room.

If your renovations increased the size of the house you might need to increase the size of your heating system to keep up.

I agree with Naomie. What kind of renovations? Were heating pipes or vents removed? Was insulation tampered with and not replaced? Was insulation added where it was needed?

Having lived in the far north of Canada, freezing pipes were always an issue. Once they came out with heated tape.... everyone went that route to keep them from freezing. They also make a foam insulation sleeve you can put over the pipes. https://www.truevalue.com/4-pack-3-ft-foam-pre-slit-pipe-insulation-for-1-2-inch-copper-pipe

https://www.truevalue.com/pipe-heating-cable-self-regulating-5-ft

Is your house on a basement or over a crawl space? I would check the insulation on the floor plate and rim joists, you can insulate .... https://www.youtube.com/watch?v=9hDNaZffAb4

If you have a crawl space, is the floor underneath insulated? https://www.youtube.com/watch?v=5rjyrSipAMo

If your water heater is in a cold basement or outside cabinet, I would insulate it with a blanket and also do the pipes if they are along a cold wall.

I agree with Namoie and William's suggestions too.

Thsi was really eye opening. Thank you evryone