Just finished having oak hardwood floors installed in brand new house and came back today and found buckling in numerous places throughout the house. The heating and a/c is not hooked up yet.
This is a great deviation from normal construction practices. The hardwood is not even delivered to the job until all the drywall is primed and the heat system has been on for at least 2-3 weeks. And two months after any concrete work is done. This is because the oak flooring is kiln dried to 6-9% depending on your climate. This is the average for indoor wood moisture equilibrium. Wood is hygroscopic it will absorb moisture from surrounding objects.
Now when this very dry wood is let to acclimatize in a virtual outdoor environment (like your unheated house), the wood can rise in MC to as much as 10-15%, this is why it swelled. It may not shrink back into place, it depends on how well it was nailed and how long it has been exposed. When it does shrink it might have large gaps between the boards and might squeak quite a bit. The nails will have been pulled out of their holes. You should get a moisture meter and measure this yourself. Keep a written record of the events. You can mail order a wood moisture meter at http://www.leevalley.com/wood/page.asp?SID=&ccurrency=1&page=32548&category=1,43513,45788.
I buy a lot of my tools from Lee Valley, and own such a meter myself. You will need to find the average indoor wood MC that is recommend for your area. Most wood floor guys know this, and all cabinet making shops do also. It should be common knowledge in the trade.
If you are very lucky and get the heating system operating right away (or even some space heaters) you may be able to bring the MC down without causing too many cracks. If you are lucky. If not you may have to replace all the floor.
As always your Most humble servant, Joseph, the Wood Floor Doctor.