To presume that homes with timber floors will require double glazing is a fallacy
Depending upon the site slope & the soil type, a timber floored home [with insulation] can often be more economical to build than a concrete slab floor, and also have a higher thermal value.
Although the overall thermal performance of the envelope of a home is by no means as simplistic as this, the presumtion or inference that in all situations timber floored homes are less thermally efficient is wrong.
It is for good reason that the HIA has been lobbying for 2 years against the imposition of 5 Star on timber floored dwellings and that is that they do rate worse than a slab.
Windows are the major energy leak in any home. This is evidenced by the fact that in the year 2000 the 2m x 1.8m window was 32% of total window and door demand in new homes - but today it is not in the top 5 windows. Why? Because design has been compromised by the 5 Star demands causing windows to get smaller - and that is in a predominantly slab construction. Timber floors make the matter worse. Of course you can build a 5 star rated home on stumps without double glazing... but you will pay more elsewhere and your design will need major compromise to achieve this. My argument is an economic one - double glazed windows (even better in a thermally efficient frame i.e. uPVC or thermally broken aluminium) are a good economic method of achieving 5 Star compliance with the least impact on house design. Plus double glazing adds comfort in temperature moderation and sound attenuation. Why avoid double glazing and substitute insulation when double glazing opens up so many more opportunities in design and comfort? In the USA & Europe it's a standard - it will be here soon. Ed