On Tue, 6 Dec 2016 22:25:53 +0000, Tim Lamb
wrote:

Upstairs life gets expensive and difficult. All the suppliers call for
insulation below and in contact with the heated floor. In a chalet
bungalow, there is no such thing as a standard floor joist spacing. The
dormer cheeks are double or triple timbered and the intervening space
filled with ladder work on joist hangers. Elsewhere walls have double
supporting timbers.

The upstairs under floor heating here has the heating pipes clipped in
thin aluminium sheets to act as heat spreaders. The heat spreaders
were cut to fit odd shapes. Insulation is fibreglass laid below them.
The flooring chipboard is fixed on top.

Upstairs under floor heating is generally much less critical than
downstairs as the downstairs heat rises and (assuming a well insulated
house) keeps the upper floor at a constant and slightly lower
temperature than downstairs even with no upstairs heating.