Documents what some builders have said about problems with moisture, soot and IAQ in relation to unvented gas fireplaces. Unvented gas fireplaces have become popular recently in the US due to their low cost and flexibility in installation. However many building scientists and indoor air quality professionals have warned against their use because discharging combustion by products into the home invites serious moisture and IAQ problems.
Are unvented fireplaces too hot to handle?
USA, Energy Design Update, Vol 21, No 10, pp 1-3.