R value increase with Tyvek 14-S (Metalized 1443-R)?

if you sleep directly on it, it adds no R value

there has to be an air layer next to the aluminized surface.  In a Neoair air pad, they have a suspended layer of aluminized material with an air layer on both sides – that provides a lot of insulation

if you put an aluminized on the outside, that works, because there’s an air layer outside that.  But not so much if you’re wearing an insulated jacket or sleeping bag – the outside surface will be close to ambient without the aluminized material, so you’re not radiating a lot of heat anyway.

If you just got done running a marathon, your outside surface would be hot, so you’d be radiating heat like crazy – an aluminized layer on the outside would be very good.

Of course, with an aluminized layer, you’re totally waterproof, which is good and bad

The metalized surface can help with radiative heat loss where it would reflect back the heat radiation. This is probably what Jerry means with the air layer as heat is primarily transferred trough air by means of heat radiation. (Note that there is conductive heat transfer in air as well. but it is neglectably low. Only vacum has not conductive heat transfer for obvious reasons.)

However, for conductive heat loss, which I presume to be the primary mode of heat transfer in a ground sheet, the benefit is a bit fuzzy to me. Normaly the conductive heat transfer in metal is higher then in plastic and could be a negative factor. What is unclear for me here is if the transfer resistance (meaning that heat does not transfer well over surface boundaries) between the metal and the tyvek can compensate for that and would need a controlled experiment ;-). Said that, i “naively” presume, and totatly unscientific, that nobody would produce a tyvek with metal if there would not be any advantage (but this could assume that it is done on a  surface(wall) where there is some radivate heat to reflect back).

To summarize I would create a hypothesis, without then measuring which is obviously totaly unscientific, that your gain is, if anything, small in a ground sheet.

It’d make a cool kite.

It can double as a signaling device.

I use a piece of Al DCF for an emergency tarp and for shade. I’ve placed it over the net in my tent, tying it to the trekking poles. I don’t know how much warmth it adds. It’s an odd fit, being a rectangular tarp in an offset tent, but it could be cut to fit.

I’m thinking curtain material for my topper.

another thing is even though that material looks reflective, it may not be reflective in IR.  You’d have to measure it.