I live in a very dry climate (Southern Colorado). We commonly run a swamp cooler all summer and various humidifiers the rest of the year. In bad weather we dry laundry on lines in the house, have teenagers who like long showers, etc. Our old house has the bathroom vent blowing damp shower air straight onto the bottom of the old 1×10 roof sheeting. It’s been that way for at least ten years and their is no sign of dampened insulation under it, water stains on the roof sheeting, etc. There is minimal attic ventilation by any modern standards. Given these conditions, I’d love to get some feedback from anyone who has dealt with ventilation issues in a similar climate.
We are planning to build a new home a couple of blocks from our current place. I’ve read various articles over the years about proper venting, both in the living space and in the attic. In my climate, is it still important to plan for lots of living space ventilation in the baths? What about venting interior air straight into the attic?
Replies
Hiya Hasbeen,
I lived in Kremmling and in Montrose from '76 to '87 or '88. I'm familiar with your climate. The overall external climate has little to do with the micro-climate that is your house. The greater impact on you answer has to do with the temperature and humidity differential between inside and outside. My guess is that your present old house is able to breathe in old ways, letting most of the mositure escape without causing damage. You are lucky.
While living there, I often found owners who puposely disconnected dryeer vents to keep heat and humidity in the house, only to discover a year or two later, that they had created expensive repair problems.
To really understand the whole science of this moisture and insulation situation, you would do well to buy Joe Lsitburek's book on building science. I don't have the link.
What elevation are you at? A couple thousand feet can make a big difference.
Excellence is its own reward!
Thanks for your reply to both of my inquiries. I live at 6,200 feet in an area that get about 14" of precip per year.
It seems to me that the foam block foundation doesn't really work well with passvie solar because the heat can't get back and forth from air to contrete in a daily cycle.
That's a good point. How do you plan to insulate then?
The ones that I remember have masonry floors for mass also and interior walls to storte and release with the exteriors well insulated. A couple used CMUs as a double wall and 4" of foam in between. I'm not sure that deals with all the moisture concerns though.
At your southern location and low elevation you might want to look at the book for moderate climates.
You are designing a whole entire package is why I hesitate to advise on one portion alone. The whole house needs to work together. You have different systems that sometimes compete with each other. Keep that in mind. .
Excellence is its own reward!
I plan to insulate with 2" foam on the outside of the block (or concrete).
I'm building a very simple rectangular home and shooting for the lowest price, partly because it's what we can currently afford (hate big mortagages!) and, secondarily, because I'm a solar proponent of sorts: If all solar homes a big fancy places that use high cost/high tech designs and materials (especially the glazing material) then the average guy/gal will remain dependent on the "bleeping" petroleum trade. I hope to develope a simple, yet fully functional, solar design that could be the "Model T" solar home design for others.
And yes, I wholeheartedly agree: Excellence is its own reward!
Thanks again, Hasbeen
How far you be from me here in Durango?
Takes us about 3 hours (unless the RV crowd is congesting Wolf Creek Pass) to get to Pagosa for our intermittent pilgrimages to the Hot Springs. Hwy 160 miles are about 200 or a little more from here to Durango. We used to love hanging out in your area 20 or 25 years ago!
Hi Hasbeen-
I restore here in the southwest. Albuquerque now, previous 10 years up in the White Mtns in AZ.
What type of roof are you going to put on your new place? What are the interior finishes going to be? What type of windows?
As mentioned, Lstiburek's books are a great help. What they emphasized to me is that there are few absolutes and what's paramount is how the suite of selected materials harmonize and anticipate effects.
Hereabouts, where Sun's strength is so great, microclimate effects are everything: think of the grass up the south side and the PJ just behind the ridge and covering the far moister north side. Same with our structures. South side stucco will be put through a much broader cycle than shaded or north. Expect southside portland stucco over frame to craze. Southside roofs melt off soon as clouds part, north side will ice at the eaves. Attic condensation will evaporate and evacuate as soon as Sun sets the roof to creaking- If the roof is inherently well vented. 26 gauge corrugated over purlins and rafters, well flashed and screwed will take anything you can throw at it, especially if you vent at the frieze-blocking (bird-blocking) and use the ridge cap designed for hips, which, without matching corrugations allows for great venting at the ridge.
Lance
Thanks for your input. My climate is very similar to yours. Rules always need to be adjusted according to the microclimate. No matter what other decisions I make, there will be lots of attic venting!