July 5, 2017

IDEAL Window Installation – Improving Best Practices



You bought high-performance windows, but is the install going to complement their performance or detract from it? The enclosure insulation, airtightness and moisture control should be continuous. But too often where the window frame meets the building we see breaks in insulation, air leaks and vapor traps – all setting the stage for discomfort, inefficiency and moisture damages. The ubiquitous can of Great Stuff by Dow Chemical provides a connection that is neither airtight or healthy – with foam residue and waste chemicals left to bioaccumulate in our environment already choking on plastic.

Makes good toxic garbage.

Cans makes good long-term toxic garbage.

We can improve our window install by using more natural, safe and healthy materials that are easier to install and more reliably durable for the long term. No builder likes struggling to insulate around windows with messy spray foam insulation or backer rod and caulk. These options are tough to install well, and are often vapor closed, short term, and generate a lot of waste. Stop it. There is a better way. You might say we have an IDEAL solution based on Havelock Sheep’s Wool insulation and Pro Clima tapes: we packaged it into the Ideal Window Install Kit.

The IDEAL window install package

We like simplicity.


Add sheep’s wool insulation around the window frame to ensure insulation continuity. And improve the performance of your windows with > R-4/in. surrounding the window frame. The sheep’s wool is easy to handle, doesn’t itch and is hygroscopic.


Managing moisture is crucial to long-term durability, so not only do the Pro Clima tapes manage moisture, so too does the sheep’s wool. It will not rot or foster mold, and it helps buffer moisture, increasing drying safety buffer and helping ensure long-term durability.

Ease of Install

Installing wool insulation around the window frame doesn’t require any protective equipment, won’t make your hands itchy, and is quick and simple to install. Add Pro Clima fleece-backed tapes for a finish that is clean and doesn’t require scraping out a mess of expanded spray foam.


Installing Pro Clima’s airtight tapes in an airtight manner allows us to keep the insulation airtight and performing to its optimal level. Continuous, verifiable airtightness also limits heat loss, improves comfort, and prevents unplanned moisture intrusion and damages where thermal bridges and condensing surfaces are most likely to be found.


Pro Clima’s tapes and Havelock sheep’s wool insulation are VOC-free, and have achieved the DECLARE label from the International Living Futures Institute. Additionally sheep wool  is a non-toxic, renewable material that actively filters toxins, absorbing VOCs like formaldehyde. This is what doing better looks like.

The combination of Pro Clima and Havelock optimizes the assembly.

The Install Sequence

The installation process is quick, clean and simple. Just three easy steps:

First – Water protection at the sill.
Prepare the rough opening and properly set the window in place. We recommend EXTOSEAL Encors as a watertight sill tape, along with the right Pro Clima window tape designed for the substrate and the taping style you prefer. Keeping it all within the Pro Clima family provides a 10-year System Warranty.

Acrylic Butyl adhesive tape - the EXTOSEAL Encors is the ideal sill tape.

Acrylic-Butyl adhesive tape – EXTOSEAL Encors is the ideal sill tape.

Second – Insulate with Havelock Wool.
From the interior side, use Havelock sheep’s wool insulation (loose-fill or batts cut to 4” wide) around the window perimeter using a Pro Clima PRESSFIX applicator, a flat bar, or a carpenter’s pencil.

Loose-fill or batt, Havelock Wool is a natural, comfortable and effective installation solution.

Loose-fill or batt, Havelock Wool is a natural, comfortable and effective installation solution.

Finally – Air and vapor control with Pro Clima tapes.
On the interior side, use Pro Clima’s TESCON Profil, TESCON Profect or vapor retarding CONTEGA Solido SL tape to connect the window frame to the inboard airtight layer – either INTELLO Plus or the plywood buck. Make pre-folded corners per our guide to ensure continuity between sill/head and jamb leg taping. On the exterior side, you can also use Pro Clima’s TESCON ProfilTESCON Profect or use waterproof + vapor open CONTEGA Solido EXO tape to connect the window frame to the outboard airtight layer: one of the Solitex membranes.

For a full explanation of window installation possibilities see our post: How To Prepare For High Performance Windows.

TESCON Profil with split backing for ease of installation at tight inside corners.

TESCON Profil with split backing for ease of installation at tight inside corners.


Durable, healthy and efficient, the IDEAL window package is a simple and straightforward approach to ensuring a high-performance install of your high-performance window. Choose Havelock Wool and Pro Clima Tape. You can find a pre-packaged window install kit ready for installation right here.

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2 Responses to IDEAL Window Installation – Improving Best Practices

  1. Mark Pollard July 15, 2017 at 7:04 am #

    Why are you advocating for the very small gap between framing and the window unit to be vapor open?

    Window units are almost always vapor closed by the nature of their construction. Most high performance windows are vinyl, PVC, u-PVC; impermeable plastic. There are a few manufacturers of high performance wood units but many of those come with aluminum cladding on the exterior.

    Exctoseal Encors is a vapor closed tape due to it’s elastic foil carrier facing, so using it as a pan flashing negates any efficacy of vapor open insulation and tape to seal the sill of a window. If the legs and head of the RO were flashed with a vapor open membrane/tape, then I can see the point of maintaining the continuity of the vapor control layer by sealing the unit at the legs and head with a vapor open product.

    Most window manufacturers call out a gap of ¼-⅜” between the framing and window unit. What “vapor trap” problem are you hoping to solve by using your system. A builder of high performance homes is going to pay particularly close attention, to among other things, window and door air sealing. If this small gap is completely sealed via lambs wool/tape, or backer rod/caulk, or (heaven forbid) foam, there really isn’t an issue. The only time any of those methods fail is when something has gone drastically wrong; large movement within the structure, bulk water intrusion, etc.

    The “Not Ideal” photo at the beginning of the article show someone doing a sloppy job trying to seal a window with a can of straw foam. It’s cute. High performance builders use gun foam, it’s much easier to control. Straw foam is for the big box clientele or slap and dash builders. Environmentally conscious high performance builders use foam sparingly or not at all, such as your website advocates for. In the photo above, they are sealing around shim blocks and the metal straps which help the window resist the in/out movement from wind loads. Have you ever tried to economically (time and materials) tape around those? Many of the high performance window manufacturers require straps for the installation of their larger units. These are an absolute bear to tape cleanly, which results in even more time spent maintaining the continuity of the air control layer by chasing the leaks during a blower door test.

    Will you be doing a cradle to grave and environmental assessment of the impact of the plastics used to manufacturer the membranes and tapes your website/business advocates for? It’s all plastic, my friends. It’s crude oil pumped from the ground, chemically broken into constituent parts, and chemically rebuilt to our liking. Plastic is plastic is plastic.

    That said, keep up the great work informing the building world and pushing for higher performance. We’re going in the right direction but, you know, plastic.

  2. Floris July 17, 2017 at 2:14 pm #

    Mark, thanks for your thoughtful response. We agree, less plastic is better – hence we offer ProClima’s DB+ as a interior smart vapor retarder that is paper based. We try to use less oil based materials, and still be super efficient (reducing oil dependence) and durable/mold free above all. The resources used for membranes and tapes offset their embodied energy very fast (months).

    The latter is also the reason to seal both sides of the vapor closed window frames – spend a lit (oil based adhesive – safe a lot of energy!).
    The gap next to these frames (wood windows ideally – free of thermal bridges like Bewiso frames) should be insulated. Otherwise the gaps around your windows will lead to very significant heat losses around your windows (ie thermal bridges that can cause condensation issues in those gaps (if only air-sealed on the outside).

    Sealing airtight on the inside with Proclima tapes, will keep the humid winter air out of this insulated cavity.
    Flashing with water resistant, vapor open tape on the outside, will keep bulk water out, but also allow outward drying.

    At the sill, we have an interesting challenge, as you point out. We want a waterproof (sloped) sill, that we make with EXTOSEAL ENCORS. The ENCORS can go under the frame to a back dam – this then allows the frame to be sealed to the ENCORS with vapor open Proclima tape (TESCON/CONTEGA).
    We do indeed stop the ENCORS after it folds over the face of the exterior WRB after 1″ – this so that any water vapor can dry out under/around it. This is much saver, than your conventional super wide vapor closed window flashing normally recommended in USA (6-9″ wide over WRB). With such width you indeed can trap vapor and create durability issues.

    Of course the space under the window frame should also be insulated as well – many projects leave this space un-insulated. This is a huge thermal bridge, leads to additional heating/cooling demand (oil use) and also creates a cold spot at the inside of the window – risk of condensation.

    Brackets should be airsealed as well – this can be done quite well with tapes. Either blind taping them with CONTEGA SOLIDO SL-D (install brackets – than tape over them, before installing window in the opening) – or encapsulate brackets behind INTELLO and tape, after window is installed + insulated. Many ways to deal with those brackets by working diligently (a high performance window, should have a high performance/quality install and airseal to get the highest performance form it).

    In the end, we wall try to make high performance buildings, with less plastic and more renewable resources. As a result we focus for that first ‘fossil fuel free”/renewable insulation and structures (think wood fiber insulation, CLT, etc). Less is best….

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