We live in Toronto, Canada. A contractor just finished installing our hardwood floors (unfinished maple 3 and 1/4 shorts which he subsequently sanded and finished). We've noticed thin cracks between many of the planks. He tells us that the cause of the cracks is the heater being on full blast due to our unusually cold winter. He assures us that the wood will expand and the cracks will dissapear once the heater is turned off. In the meantime he suggests that we buy a humidifier to deal with the problem. Is this right?