You could add gravel fill to raise the floor of the crawlspace to be above drains.
Posted: 10:22 pm on September 22nd 2018
The plastic on the floor will prevent moisture from rising into the crawlspace even if there is water. Gravel fill also adds radon mitigation options (if needed).
Posted: 01:00 pm on September 23rd 2018
The 2018 IRC refers to NFPA 275 in R316.4, so it appears to be the right test (but local requirements may differ).
Posted: 01:18 pm on September 23rd 2018
Ventilation is about not breathing polluted air and humidity is a horribly inaccurate way to gauge this. Your house is tight enough to need mechanical ventilation. A centralized ventilation system and open interior doors will save money and be better than what you have. The TwinFresh Comfo may be useful where you want to close doors. I haven't done the calculation, but I'd guess around 70 CFM running whenever the house is occupied.
Posted: 01:16 pm on September 24th 2018
You are well under the 5ACH@50 where you might consider not using mechanical ventilation. 2018 IMC, 401.2. Once you fix this, I doubt you will have problems with Winter humidity being too high.
Posted: 02:03 pm on September 24th 2018
Even if you block attic vents, a semi-conditioned attic (some insulation on the floor, some above) is not a good idea. Be sure to air seal.
Posted: 09:52 am on September 25th 2018
There is no doubt that a zoned source in every room provides more control and comfort than a "point source per floor". But I'm not aware of any tools that accurately predict how well a centrally located source will heat some back room at the end of a hallway. It certainly won't give you the option of keeping that back room a couple of degrees warmer than the central room.
Posted: 11:36 am on September 25th 2018
Also consider the permeability to moisture. In most cases, I'd prefer some permeability to the nearly none of foil.
Posted: 01:04 pm on September 25th 2018
It's good to see a shift away from ZNE towards metrics that better measure what matters. But more needs to be done on wider scale cost effectiveness. Ie, if building design can save a ton of carbon for $X and some other approach can save the same ton for $.5X, then focus on the latter.
Posted: 01:39 pm on September 25th 2018
Note that Dana said "unfaced EPS". Faced EPS and poly leaves basically no ability to dry in either direction.
Posted: 02:18 pm on September 25th 2018