How to add an extra layer of insulation?

haileystoop

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? 

  

EricL

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