Temperature Discrepancies.

[UFH-newB]

I have a new build house with ground floor wet Heatmiser UFH. Over the past year I have noticed that in summer, an indicated Neostat V2 room temperature of 19C of higher feels very comfortable in a short sleeved shirt. However in winter, the same indicated temperature, 19C, feels cold enough to need to put a jumper on. So I took separate temperature measurements from summer onward. On a warm day the Neostat temperature and the measure temperature were the same, +- 1/2Deg C. However now, with an indicated Neostat room temperature of 19C, an independent measurement in the room shows anything between 16C and 18C. The only way I can get the temperatures to agree again is to manually turn on the UFH in that room, or crank the Neostat setting up to 20C or 21C, wait until the room catches up a couple of hours later, then turn the setting back down again. Is this sort of behaviour typical, and if so, can it be avoided in some way?

[JohnMo]

What are you using to read the independent temperature?

[vala]

Higher humidity in the winter?

[Conor]

In winter, walls and windows of the house will be colder than this, you feel this through the slight conventions and radiant heat loss. 

 

There's a setting in the neostat where you can change the start / off points. Default is something like 1.5c, change it to 0.5.,

[Andehh]

For what it's worth OP, I'm dealing with this myself!

 

The house retains heat well, but exactly as you say... 20 degrees feels more like 17 degrees!

[mike2016]

Did you get an air tightness test performed, if so what score? What type of ventilation system is there? Do you have trickle window vents, a stove / flue or leave interior doors open or closed a lot? Sounds like air movement of colder air, maybe stratification disturbing the layer of air around your body. Try a thermal camera and test temps at different heights in the room.

[Alan Ambrose]

You don’t say how you’re measuring, but you need a fairly accurate measuring device (not cheap) and to measure just under the stat at the inlet where the air runs past the built-in thermistor. The effects you see are probably due to room variation, thermistors don’t drift much. I’ve installed a couple of Heatmiser set-ups and I usually commission by going round to each stat, measure the temperature by the stat with an accurate device and use the in-stat menus to make the stats match the actual reading. As others have said, maybe the difference is air movement, sun or humidity.

[JohnMo]

1 hour ago, Andehh said:

For what it's worth OP, I'm dealing with this myself!

 

The house retains heat well, but exactly as you say... 20 degrees feels more like 17 degrees!

When you read up on passivhaus design, they explain why different concepts developed, where the U values come from etc. One of the topics is glazing, and how the glazing affects the way the room feels. Across the glazing there is a temperature gradient between inside and outside air temperature and depending on the U value, is where the inside of the glass settles temperature wise. The lower the U value the closer it is to room temperature. The glass can suck the heat away from your body. Imagine an Infrared heater in reverse, your body being the heater the window being the body being heated, the lower the glass temperature inside the more it extracts heats. Same is true for the external walls also.

 

Passivhaus push triple glazing because irrespective of outside temp the inside of the glass is alway within a degree or 2 of the room temperature. So the window doesn't affect the way your body responds to the actual room temperature.

 

That is the principal reason why we feel can feel differently in the same room temperature, the heat is being sucked out of you.

Edited October 29, 2023 by JohnMo

[Andehh]

Interesting, thanks for that.

 

We have a lot of glazing all over the place, which we've never had before so taking some getting used to.

[patp]

Are you used to having radiators? If so I think it is fairly well recorded that underfloor heating takes some getting used to. We are finding this to be the case.