How do you insulate a cottage crawlspace? It's in the Haliburton Highlands
Our cottage is on concrete piers. The cottage crawlspace is uneven ranging from 30-36 inches. Exterior of crawlspace surrounded by pressure treated plywood skirting which has multiple vents. The dirt floor is well covered with heavy guage plastic. There is pink batt insulation between joists. The cottage crawlspace is divided in half by a styrofoam boundary. One half has all the plumbing, 2 radiators, spray foam around perimeter and a dehumidifier with hose exiting to outside. The vents on this side have been sprayed shut with the foam.
From reading the other posts on this site, we wonder if a) we should close all the vents, b) remove the pink insulation to reduce humidity, c) remove the styrofoam boundary from underneath, and d) spray insulation on entire perimeter of plywood skirting?
Would moisture problems under cottage contribute to moisture inside cottage? We would like to reduce moisture and keep the cottage as warm as possible because we are living here part-time throughout the year.
First I'd suggest you start here on our page on how to insulate crawl spaces –
How to insulate crawlspaces properly
Venting a crawlspace can be a problem if there is high humidity outdoors and that humid air hits the cold surfaces of a crawlspace or basement as it can lead to condensation forming. Is your dehumidifier a fairly modern one that shows a reading of the current levels of relative humidity?
Its’ best to keep them below 50% RH if possible, certainly below 60%. You have a few questions going on here so I’ll do my best to answer - The insulation won’t ‘add’ humidity, but it’s only needed if you’re heating above and not heating below. If you have insulation batts I assume you may be keeping it cooler down there. Is your plywood touching the ground inside or out? Does it extend below grade? Pressure treating wood will extend the life but it’s still wood and still subject to rotting at some point, so applying spray foam to it may not last very long.
As for your last question, yes, moisture below your cottage will for sure add moisture to the conditioned space above. Best is to lay down a sheet of 6-mil (or thicker) polyethylene vapour barrier to the ground below so moisture doesn’t evaporate into the crawlspace and then the house. Once you’ve had a look at our crawlspace guide pages you may have some better insight, and more questions as well.