Designing for a cool, humid climate – GreenBuildingAdvisor

I’ve been asked to help with a design in Newport County, RI. Newport is a popular summer destination because it’s cool by the ocean, you can have your windows open and enjoy the sea breeze. But it’s also very humid, mold and mildew are a major concern.

Some stats: 

For June, average temperature is 66F, high of 73F and low of 59F

July is 72/79/65

August is 71/78/64

According to the ASHRA Design Conditions database (which is a great resource, https://ashrae-meteo.info/v3.0/index.php )

the 99% cooling design temperature is 81.5F. The 99 percentile humidity is a dew point of 72.4F with a mean coincident dry bulb of 76.4F, which equates to a relative humidity of 87%. Mean annual maximum temperature is 89F. 

So this is a climate where air conditioning is barely needed, but it’s wicked humid, as they say in the local vernacular. At night you almost always want to sleep with the windows open, even though sometimes the fog is so thick it sets off smoke detectors.

The homeowner is adamant they want to keep the windows open on all but the hottest days.

The house will be winterized and heated in the winter.

I’m trying to think of how to approach this to avoid the house becoming a moldy mess. Obviously any surface that is colder than ambient has to be insulated. 

Thoughts?