You’re building a high-performance, low energy building – maybe even a Passive House.
What’s the Problem?
You started construction in the summer, but by late Fall or Winter the finishes are being installed and the indoor relative humidity (RH) is high – reaching 90%. You know the vapor drive is going out and the wood framing was delivered wet to begin with, the concrete is still drying, and the tiling and drywall spackling is making you worry about the potential for moisture loading of the enclosure.
The question is simple: How do you protect your high-performance assembly from moisture damages with a humid interior, during construction, in colder months?*
Luckily the answer is simple too: Install an INTELLO smart vapor retarder.
Why? Because INTELLO provides reliable performance – preventing moisture loading of the enclosure in colder months and allowing inward drying in warmer months. Through seasonal changes in vapor drive, the enclosure builds drying reserves and a safety buffer. In fact, INTELLO provides the most powerful protection available on the market today.
It’s a fact that INTELLO is the best, not because we’re saying it, but because among other reasons, it’s the only vapor variable membrane to meet the stringent standards of the German Institute of Construction Engineering (Deutsches Institut für Bautechnik, DIBt), which is the body responsible for technical approval for construction products in Germany. In fact, INTELLO is so good, DIBt has also approved it for use in unvented hot roofs.
A critical aspect of meeting the approval is the shape of the variability curve (how quickly the membrane opens or closes under increasing or decreasing humidity), and how the material works under construction stresses.
Why is INTELLO Best in Fall & Winter?
During construction in colder months, when the interior of the building is at 90% RH, and the RH inside the insulation directly outboard of the INTELLO might conceivably be as high as 50%, the average RH at the membrane is 70%.
The German building code standard DIN 68800-2 requires that at 70% average RH, the vapor variable membrane’s permeability should not exceed 2.2 perms, yet not fall below 1.3 perms. At Pro Clima and 475 we call materials meeting this threshold HYDROSAFE.
We call it HYDROSAFE, because even in these challenging conditions, a 2.2 perm rating is retarding enough to avoid further damaging levels of moisture loading. And it must not be below 1.3 perms, to guarantee the long term protection and durability during occupancy of the building.
INTELLO is HYDROSAFE, with an optimized perm rating, at the sweet spot of 1.6 at 70% RH – providing maximum protection during construction and then during occupancy. So the shape of the curve is important.
Next, the question is the drying potential – and with the greatest vapor variability on the market at a factor of 100 – INTELLO provides maximum drying capability when warmer months arrive. So the range of the vapor permeability curve is important too. We see this drying capability in real life experience.
Don’t Go The Wrong Way
So INTELLO is reliable and proven by data – but you can’t help asking: Okay, can we improve on this vapor control?
- Vapor closed, like poly? Forget about it (a recipe for mold and moisture damages, when the impermeable poly doesn’t allow inward drying in the summer)
- Reduce the variability, making the maximum drying capacity less than 5 perms, so when it’s fully open you’re trying to dry through the low range of a class III vapor retarder? Bad idea
- Allow it to open up quicker? Let’s not go there – you don’t want to load your assemblies with vapor when the interior is at a healthy 50%RH
- Give the vapor permeability a direction? Nyet, Vladimir. (And don’t install it backward or the non-improvement can have unintended negative consequences.)
- Make it vapor open? Better not to un-protect your assemblies
*Opening windows and dehumidifiers should be employed to try to limit interior RH to 50-60%, however spikes are most likely unavoidable and need HYDROSAFE protection.
In the meantime, don’t make problems for yourself. Get the best protection. Get INTELLO.
Related Blog Posts
- The INTELLO Primer
- Why The Vapor Curve Matters
- Drive Safe, Build Safe
- How And When Smart Vapor Retarders Should Open Up; INTELLO’s Decade+ Of Safe Construction
- Can’t vent at valleys and dormers? Use a smart vapor retarder (not foam)
- Do More With Less: Your Dense Pack Netting Should Multitask
- Project Spotlight; INTELLO Plus with & Integrated Service Cavity in Leicester VT
- INTELLO Plus transforms assisted living facility in Mashpee, MA
- Builder Testimonial: Brad Hankins on the INTELLO Energy Revolution