MIL not sleeping over our house being too cold

The optimum temperature for sleep is 16-18 degrees so whilst on the lower end of that, you are in the correct range.

During the day we have ours at 19 or 20 degrees which is warm enough for us.

All advice is that babies shouldn't sleep in rooms which are too warm, The Lullaby Trust, who advise on baby health say 16°-20° is ideal, so you're at the lower end of that, but definitely still in safe temperature range. Share the official advice with your MIL and tell her you're doing the best thing to lower risk of over-heating, SIDS etc...: www.lullabytrust.org.uk/baby-safety/safer-sleep-information/room-temperature/

I think you’re right that your mil has said her piece and now she needs to butt out. However, I also think you need to turn the heating up while your baby is so little. 19-20 during the day and then let it cool down over night if you must, but sleep close to your baby to monitor them.

My husband and I disagree on the heating/our duvet etc but when the baby was small he conceded that we had to make sure the house was warm enough for him. I think unless you’re in severe financial difficulties, your husband needs to let go of his control over the heating for a little bit.

Presume he’s also not the one who’s at home most of the time? you need to be able to make decisions about your space.

Our heating is set to come on during the day if it drops below 18 during the day/evening and 13 overnight.

16 for day/evening would be too cold for me.

Do you have a thermometer in the bedrooms? A house with a single thermostat in the hallway will often be cooler in the outer rooms, where the heat is lost much more quickly. Your bedroom could only be 13 or 14 degrees, which is far too cold.

We have ours set to 19 and that’s us being tight arses. 16 is pretty cold, and even at 19 we are all sat under blankets on the sofa. We are considering turning it up a notch!

16 is way too cool for a baby and you just be freezing !

I simply don't understand when people are too mean to put on their heating /turn it up(if they have the financial resources to do so) .
I have previously been in a position where I had no heating and no money to put it on (when I had it).
I really appreciate my lovely warm home now and never take it for granted.
Stinginess is a truly unattractive trait

As an adult I'm ok with 16c provided I don't have to sit still too long. At home it's easy to keep active. Much harder for babies and visitors to move around the house!

I wouldn't have it at 16c in autumn/winter now that I have young children. They don't always realise they're cold until they start shivering. And baby might be fine layered up but what's the room temperature for nappy changes, undressing, baths?
I'd be worried about air quality too. You can't keep windows open if you're not heating the house properly. Cold, damp, stale air grows mould spores faster than anything! Even if you can't see or smell the mould.

Our heating is currently set to come on when the main thermostat drops below 20. However, bedrooms with less sun and in particular the rooms over the garage/porch get to around 16 before the main thermostat reads below 20. Could your house be similar?

Our house obviously didn’t get that memo. Zero mould issues and the thermostat is set at 16 degrees.

It isn't unreasonable for the MIL to be worried, she's concerned about the baby and I would be too (not so much about the night time temperature but more about the house being cold during the day and the possibility of damp).
She's also worried about her son's asthma. I would be less concerned about this because he's an adult and choosing to do it to himself should he have an asthma attack. If the temperature at work falls below 16 degrees sedentary workers can refuse to work. I was in an office in an old building that was at this exact temperature, we had a thermometer on the wall. It was horrible, I couldn't concentrate, my hands were freezing. If the baby isn't always wrapped up warm in a cot he'll be miserable.

Exactly this. The guidelines are too cautious. My babies were too cold if I followed it strictly too. Essentially I work with an extra layer (short sleeved vest usually, or sleepsuit rather than long sleeved vest etc) than what they say

I dry my clothes indoors with a dehumidifier and open windows every single day
I’ve lived here 19 years, the heating is usually 16-18c and I’ve never ever had a mould issue - I air the house and the dehumidifier takes out water
21c and above is physically uncomfortable for me as I’m allergic to heat

Just to add another perspective, but it’s a new home, right? And perhaps a relatively new build? Our house is about 15 years old, well insulated and has electric heating all around. We have to set our thermostats on each radiator, which is actually quite good because we can adjust for each room. They are mostly set to 18 currently.
However, when we moved in we had to put them at 22, because the house was empty for a while before we moved in, and it takes a while for a house to properly heat up. It took us a few months to actually feel like we were warm in our own home! This was about 3 years ago. Once you’re on top of it, it’s a lot easier to maintain, but it takes a bit of effort to get there.

I’m with MIL on this . 16 is too cold 🥶

Your MIL is pissing off her son because she thinks he is being too stingy and controlling over money/heating to your detriment and that of your baby. She's also refusing point blank to come over despite it meaning not spending as much time with her grandchild to show she is serious about this.

She's on your side (well, the baby's, but yours as well).

She's a keeper.

Why don’t you put a jumper on instead of the heating? If you can tolerate 16 with a vest on, surely all you need is a light cardigan?

16 degrees!! And being sparse and a tight arse with heating. . . . It’s far too cold, almost uncomfortably so. I think ‘room temperature’ is considered to be around 20/21 degrees. If it’s too cold, it will get damp and then you will have mould appearing and that is dangerous especially for a baby. If you are parents, you need to be responsible and stop being tight, put the heating on and set the thermostat to a sensible level. Your MIL is right. Also spending money on heaters etc is more expensive on the electricity bills. You’ll feel terrible if your baby is ill come the winter, when it does get properly cold, they can’t regulate their temperature remember.

16 degrees IS too cold. Should be around 19.

No, you stated you set your thermostat is set to 16, so that's your maximum really as your heating will shut off as soon as it hits that temperature. 16 is too cold for a newborn baby. You shouldn't have to be using a 3.5tog sleepsuit. You seem to know this as you've moved rooms. Your MIL is right - put the heating on

I’m hot natured and that would be too cold for me.

I have mine at 18 but that is because we get warm quickly, other people complain my house is cold. Even I would be very cold at 16.

I've been busy around the house today in a vest top and joggers and just checked the thermostat- its 16 degrees. DD is wearing tshirt and leggings, DS shorts and hoodie. No-one is particularly cold. I'm putting the heating on now because the temp is dropping outside but by the time it gets to 19 we'll all be too warm i expect. No mould and no respiratory conditions here.

16 degrees is too cold for a baby. An acceptable room temperature is between 18-21 degrees but babies and older people need it to be a bit hotter because they don’t move as much.
I used to have ours on at around 21 degrees when the children were small. Now it’s usually between 18 and 20. When my parents and in laws come over (75+) we have to increase by a degree or 2 or they complain of being cold.

Then people wonder why the British have the highest percentage of people with respiratory problems in Europe:

• At temperatures at or below 19 degress celcius the house will develop mould even if it is well insulated and has double glazed windows in every room. (No, 5 centimetres of insulation does not equal well insulated)
• If you also dry your clothes or even some of them indoors you will risk causing mould issues in your home.
• children are more at risk for developing serious health problems from exposure to mould than adults are.
• if your immune defence system is under attack from mould, being cold will make you more likely to get ill.