We are buying our first home and it's a shell currently and it's roughly 70 years old.

I want to insulate the house as much as possible and I came up with an idea for a multi-layer approach for improved thermal insulation. I've come up with a sequence of layers and wanted to get your thoughts on its feasibility, effectiveness, and any possible improvements.

Proposed Layers (From bottom to top): Concrete Floor Base Thermal Insulating Paint Tile Adhesive XPS Board (10mm) with tape on the seams Contact Adhesive OBS Board (5mm) or Optional Plywood Thermal Paint Vinyl Sheet Flooring (4mm Padded)

Questions: Moisture Concerns: Have any of you had experience dealing with moisture issues when layering over old concrete? Should I be concerned about trapping moisture between these layers?

Material Compatibility: The XPS board can't interact with solvent-based adhesives. Is a water-based contact adhesive sufficient for securing it?

R-Value Goals: The combined estimated R-value of these layers is approximately 0.832 K·m²/W. Is this a reasonable R-value target for thermal insulation on a concrete floor in the UK's climate?

Additional Insulation Ideas: Are there other materials or techniques you'd recommend to enhance the insulation capabilities of this floor?

Code Compliance: Are there any building code considerations I should be aware of for this type of multi-layered flooring?

Durability: Given foot traffic and general wear and tear, how durable do you think this setup would be?

Cost-Effectiveness: Lastly, does this seem like a cost-effective method for enhancing insulation and comfort?

Any insights, advice, or alternative ideas would be greatly appreciated!

  • The thermo paint might be expensive for any gain. Depth of the floor below ground level? You just want the XPS not to slip/slide around, on the floor with plywood on top, bubble gum might be enough holding power. Any water stains on the floor or walls?
    – crip659
    Commented Oct 24, 2023 at 22:40
  • Welcome to Home Improvement. Please take the tour and read up on how to ask a good question, then edit this down to one, specific question. Feel free to hit the "ask question" button more than once, but this is too broad to ask all in one shot as is.
    – FreeMan
    Commented Oct 24, 2023 at 22:52
  • 1
    I'd be far more concerned with (and willing to spend money on) insulating the walls really well, and sealing around and possibly replacing (depending on age and type) the windows much more than lots of insulation on the floor. While the floor can/does get hot and cold, unless you have an open crawlspace underneath i will be more or less ground temperature, as opposed to the walls which end up at air temperature which tends to be far more extreme both in summer and winter. Commented Oct 24, 2023 at 22:57
  • 3
    Move the insulating paint money into something else. An extra eighth inch of XPS would provide you more insulation value. Tile adhesive doesn't play well with water, and a slab surface is commonly a water source. It would be best to treat the XPS as a vapor barrier. Everything below it should be moisture resistant.
    – popham
    Commented Oct 25, 2023 at 0:40
  • substitute some sort of solvent resistant foam for the XPS.
    – Jasen
    Commented Oct 25, 2023 at 1:59


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