Hi, we are building a new house, will be installing an indoor boiler but have not chosen the brand yet. Contractor wants to install the flue and get chimney sealed up for winter and is wondering what size pipe. From what I've read, there's a whole variety of flue sizes from 8" to 5"! We have over 30ft vertical on the final pipe, so draw should not be an issue. Should we tell him go with 8", then do some sort of converter fitting to reduce size down to the boiler if we need to? Sorry, still learning about this!