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I currently have underfloor insulation but still find the house cold in winter. There is a full concrete basement which gets damp in winter , I suspect this is why the house is still cold even with the minimum requirement of insulation underfloor.
there is sufficient roof insulation. But no wall insulation.
house is heated by heat pump.
we are in south Otago
my question is , how can I keep the house warm in winter? Do I add an extra layer of insulation underfloor? If so, what R rating? Do I staple a layer of polythene to the joists in the basement? What are your suggestions?
Hello @haileystoop
Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about your insulation.
Thank you for the clear photos and the detailed explanation. From what you’ve described, it sounds like you’ve already done a good job with insulation in the ceiling and under the floor, but the persistent coldness is likely coming from the combination of a damp, uninsulated basement and heat loss through uninsulated walls.
Concrete basements tend to absorb and hold moisture, which cools the air and draws heat down from the rooms above. This effect can make even a well-insulated floor feel cold because the insulation slows heat transfer, but it can’t stop the overall cooling influence of damp air below. The first and most effective step is to control the dampness. Make sure there is good ventilation in the basement and consider installing a dehumidifier during the winter months. You could also line the concrete walls with a moisture barrier such as heavy-duty builder’s plastic (polythene), securely fastened and sealed, to reduce rising moisture and condensation.
Adding an extra layer of underfloor insulation might be possible and can be helpful, but it’s important to do it safely and effectively. I propose engaging the services of a professional insulation installer and asking them about the possibility of installing secondary insulation such as Expol 1240 x 410 x 60mm Polystyrene Insulation Panel - 11.
Let me call on our experienced members @Nailbag, @Dave-1 and @AlanM52 for their recommendations.
If you have any other questions we can help with, please let us know.
Eric
Good Evening @haileystoop
Had to look up where you guys were 
And yep you would get cold for sure.
I saw the insulation rating and had a squiz at what NSW would be, min recommended is R2. and for Sydney R2.5. From looking at your insulation pics I would add another layer to them, making sure that it is firmly fitted between the joists, without dips of narrow points as this will allow the cold to penetrate easily.
I like @EricL's suggestion of a dehumidifier for winter in the basement. That plus thickening the insulation hopefully will make your place warmer. It would be interesting to see what the temps are if you happen to chart them pre doing anything and then afterwards
Dave
Hi @haileystoop,
Good all round advice and I like the dehumidifier suggestion.
Not sure how large that area is but this one will cover a 125 m³ area.
They all come with programmable features but I suggest.
Tapo P100 Mini Wi-Fi Smart Plug
So you can operate the unit from upstairs too manually turn on/off by tapping a button in the phone app - as needed.
The smart plug can also be programmed to auto turn on/off at particular times.
Cheers
