Hi Gumphri.The tightness of the house is not so much the problem as the balancing of the air flow with these combustible appliances. You should have a certified professional inspect or advise you on a remedy. Here are a couple of links for information purpose.

http://www.cmhc-schl.gc.ca/en/co/maho/yohoyohe/inaiqu/inaiqu_004.cfm
http://www.cmhc-schl.gc.ca/en/co/maho/enefcosa/upload/wood_heating_EN_W.pdf