[michael]

Thanks, Ryland, for your suggestions. I've spent some time looking at heat recovery systems, and they look to be good solutions to the problem of losing heat through whole house ventilation. I have to take Exeric's comments above seriously, however, such as the fact that the difference between indoor and outdoor temperature where I live is not extreme. Also, I've been thinking about our heat source which is a radiant floor (pavers over 1.5" of concrete) which holds plenty of heat, and the air in a building such as ours doesn't appear to stratify. Losing some of the slightly heated air to the outside and having it replaced by slightly cooled air from the outside won't do much to alter the essential heat of the house which resides mainly in the mass of the floor. I'm not convinced that there would anything better than an energy trade-off if we were to employ an HRV. I don't reject the idea, but I am questioning its efficacy in our situation. mm