Sliding Glass Patio Door – Leakage Rate?
Climate zone 6A and doing a pretty good home with a target leakage rate of less than 1.5ACH50. I’m just starting to look at windows so I’m not fully up on the technical specifications yet.
In the design stage I made a compromise on patio doors. I did have casement french doors originally specified as I knew they would be better for air leakage but due to trying to keep the house size as small as possible and the problems the door swings were having with layout and furniture placement I compromised and went for sliding glass patio doors. The doors are for a 12′ opening and are 4 panel with the middle two panels sliding creating a 6′ opening.
My contractor is recommending I go with Andersen 100 series windows and doors, with a fiberglass frame. Concerned initially at the air leakage through the patio doors I went to the Andersen website and I was surprised to see that the specs on their bog standard 100 series doors is the same as their fancy pants top of the line A series doors. The A series is <0.2 CFM/ft^2 (of frame) and the 100 series is also < 0.2 CFM/ft^2. Then if you look at the casement windows data sheet for air leakage of both those series it is also < 0.2 CFM/ft^2. What gives with the leakage rates being the same for casement or sliding or fancy pants windows or bog standard windows? I’m about to calculate my leakage rate through the windows for my entire house and see how that may influence my overall ACH50 numbers. OH BTW my house is at a beer can short of 7000ft altitude. Please add clarity to my world 🙂 Steve
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Steve, I don't have a good answer for your question, but assume it probably has something to do with testing conditions. I know that for most tests they use a standard-sized unit, for example. Maybe someone more knowledgeable will answer. (Does anyone know if Oberon is still around? He knows everything there is to know about windows....)
Steve,
I have a lot of Andersen 100 series casements and fixed windows. For the money, it is a great window. I also have three sliders stacked on the rear of the house (basement, first floor, and second floor). The distributor said I would be disappointed in the 100 series slider and recommended that I use the 400 series instead. I haven't regretted following his advice.
My house tested at 1.7 ACH50 without blocking any of the exhaust fan or ERV ducting.
The numbers you see are a cop out by Andersen. They do not give exact numbers, but only state that they pass the minimum required < .3cfm/ft^2. Look carefully at all the numbers, including the DP number. A 400 series four panel, 8' tall gliding patio door has a DP of 35.That means it should resist leaking water up to a 46mph wind driven rain. The 82" tall model is good up to 39mph rain. Those are kind of weak numbers, but not uncommon from most of the popular providers of doors and windows. To contrast, look at a Cascadia compression slider with .002cfm/ft^2 air leakage and wind driven rain resistance up to 78mph.
Steve,
What was different about the 400 series sliders to the 100 series? I called the Andersen tech support line (took me to 3 reps before someone could answer my questions) and they said the construction of the frame, the rolling and locking mechanisms are the same the differences are materials and colors and superficial options. I don't see anything on their website that indicates differently - there are some very minor improvements to U and SHGC so I'm interested in why the 400s over the 100s?
Kevin,
The information I found on Andersens website I could only find Performance Grade numbers and DP numbers for casement windows and gliding doors of size 71.5" x 71.5". Where did you find the numbers for a 4 panel 8' tall patio door?
How do I find what DP corresponds to in terms of the wind driven rain and will these numbers be consistent across all manufacturers so I can do cost performance comparisons?
Steve
I put a low-end Andersen series slider (not sure if series 100, it was $350 3 years ago). It was a chore to achieve square and plumb as the frame was all vinyl and flimsy. I finally got it to be minimally acceptable and moved on. It's not the door I would choose.
We put in a 12' x 8' Marvin clad slider in our current house. The frame is straight and rigid. It took 5 minutes to get it square and ready to finish out. Very impressed.
I echo the other comments re: window testing. I put casements in as I knew they should be better, even though the manufacturer shows the infiltration to be the same as double hung.
For the 4 panel https://awwebcdnprdcd.azureedge.net/-/media/aw/files/technical-docs/performance/performance-windows-patiodoors-performancegrade-airinfiltration-soundtransmissionratings--400series.pdf
From Oberon:
“The DP rating of a window or door is based on laboratory pressure testing in pounds per square foot or psf.
Air, water, structural is a three part test that determines much about a window's overall performance. Air infiltration is the first phase, water penetration is next, and structural is the third part of the test.
Windows are tested for air infiltration simulating a 25mph wind or a 1.56PSF pressure load - air infiltration is treated separately from both water infiltration and structural and it is independent of the design pressure of the unit. Said again - the air infiltration rate in a window is not based on the design pressure rating of the unit.
Both water penetration and structural testing, on the other hand, are based on the window DP rating. Water infiltration is tested at 15% of the design pressure and structural is tested at 150% of DP rating.
What this means is that a window with a DP30 is tested for water infiltration at 4.5psf (15% of 30psf) while a window with a DP40 is tested at 6psf (15% of 40).
A window with a DP30 rating should be able to keep out rain when its driven by 42mph winds and a window with a DP40 should be able to keep out rain when driven by 49mph winds...so while water infiltration is DP related - and air infiltration is not - the nature of air and water infiltration is different.
The structural rating of a window is as much about the glass as it is about the frame and sash system. In order to get a higher DP rating the window manufacturer has to consider the thickness and possible heat-strengthening (or tempering) of the glass as well as the use of higher-end hardware and good quality sealants in the frame and sash system.
But, interestingly, there is nothing in the structural rating that specifically requires that the unit be air-tight. A window can leak air like a sieve and still achieve an excellent DP rating. Likewise a window that is sealed tightly can have a lower DP rating but excellent air infiltration numbers. Obviously there are also many units that have both excellent air infiltration numbers and a satisfactory DP rating (relating to both structural strength and water infiltration).
Simply stated, the relationship between DP and windspeed is -- "the ratios of the design pressures in psf are the square of the ratios of the wind-speeds in mph".
A window with a DP30 is rated to a pressure level equivalent to a 110mph windspeed, but it is tested (for structural) at a pressure equivalent to 164mph.
A window with a DP40 is rated to a pressure level equivalent to a 127mph windspeed, but it is tested (for structural) at a pressure equivalent to 190mph.”
Formula square root of psf x 20.01=mph
Kevin,
Awesome information thank you for the informative post. I found some info regarding the Ensewiler Formula after a quick search.
Steve
The sliding glass door was my most difficult purchase. It's very difficult to find good ones and they are ridiculously expensive, even for the ones that are poorly rated!
Steve,
The rep told me the 400 series is a beefier unit. I don't recall doing a physical comparison. I do have an intus front door with triple pane glass. It is massive, and I would have gone for Intus all the way around but did not learn about its products until after the window package was ordered. If your budget allows for a better performing slider, buy it. If your budget or timeline means you need to choose Andersen, I think it will suffice for a pretty good level of house.
Is there an easy way to convert the metric (m^3/hr)m-1 to cfm/ft^2? The flow rates are easy enough, but one is based on crack length if I'm reading things correctly, the other window area.
Thanks
Steve, I have a 6' wide 100 series patio door in my house, next to a built in desk. I had a fiberglass french unit in the prints and changed it because I didnt want the inswing. It seals very well even for a single point locking mechanism. Its a pretty heavy unit. I am under .6 ach50 tested and its not a small house. Under a blower door test you will not induce noticable leakage, it is a tight unit.
400 series is beefier because its wood. But its clad with vinyl which is a garbage way to clad a window. I would get a fiberglass unit or extruded clad frame, not vinyl and not roll form. 100 series is a terrific value and they are tight.
Thanks again for the feedback everyone.