Any kind of air exchange will cause heat loss or gain, decreasing insulation. Does not matter if it's through wall or HVAC. If there is no draft, it means ther

Any kind of air exchange will cause heat loss or gain, decreasing insulation. Does not matter if it's through wall or HVAC. If there is no draft, it means there is no air circulation. The only difference is if the draft goes through HVAC vents or through unsealed doors and windows, or through walls. If your local heaters are effective and seal controllable, there should be really no difference in many municipal settings as the heating is waste heat from electricity generation anyway. (Those cooling towers "greens" love to hate.) Certain baseline air flow is strictly required and it is quite a lot, especially in small volumes. Now, if you have to burn something to heat, then by all means do install a heatpipe recovery system.