I agree with Rhizon that radiation would have an impact, but its the conduction through the wood that is the rub. I did some estimating on the heat loss though sides and bottom. Again it is true that transfer to the ocean is great, but you have to get through the wood first. I think that Rhizon's point of hibernation is an important one. Glenn's response to me on that point was that food was packed for something.
Hibernation is almost a requirement.
In designing heating for modern homes, one still assumes air leakage. Without any ventilation the ark would have smelled worse than any barn or zoo building - to the point of serious health and oxygen problems. One could even calculate the oxygen needs, and then determine a minimum air flow.