Replies

1. 
   Gene_Davis | Apr 17, 2007 02:34am | #1

   Are you questioning what something like "DPxx" means?

   If it is that you are after, it is best explained as,

   the higher the number, the better the window (or door) can resist wind-driven rain.

   The numbers, 20, 30, etc., correspond to a scale of test laboratory protocols in which the differential pressures laid on test units correspond to those reached at approximate wind speeds.  The "rainfall" spray is a constant.

   Why do you need to know all the tech details?

2. 
   rpait | Apr 17, 2007 02:49am | #2

   in addition to all of that, dp varies from location to location and is in correlation to how the home is constructed. You can email me at [email protected] if you need help selecting windows, I used to sell them(recently stopped).

1. 
   sledgehammer | Apr 17, 2007 02:58am | #3

   Actually have a customer that bought a dp20 door (not from me). It faces northwest over a large body of water. which is where our weather comes from. We just had a nor-easter blow through with 60 mph gusts. His door leaked... He thinks it's a defective door. I told him the weather is beyond what the door is made to withstand...

    

   He wants to know what the door is designed to withstand.

    

   Therefore the question.... What does dp20 mean?

1. 
   rpait | Apr 17, 2007 10:52am | #4

   it means 20 pounds per square foot is what it can withstand in terms of wind pressure.

   Design Pressure: A numerical value that defines the structural wind loading requirements (in pounds per square foot) for a building and the components and cladding of a building.

   courtesey anderson windows .com

1. 
   sledgehammer | Apr 17, 2007 03:49pm | #5

   Thanks all, but it's not really the testing they do to determine a rating I don't understand it's how the rating applies to the real world. Our weather service reports the winds in mph, not lbs/sq foot.

1. 
   BenM | Apr 17, 2007 11:44pm | #6

   20 psf is about 88 mph.  (psf=0.002558 x V squared).  V is in mph.

2. 
   sledgehammer | Apr 18, 2007 01:26am | #7

   THANK YOU!!!!

3. 
   sledgehammer | Apr 18, 2007 02:07am | #8

   Was just informed by the manufacturer that a door with a dp20 rating will leak water in a 35 mph wind.

    

   I'm back to confused.

    

4. 
   rpait | Apr 18, 2007 03:12am | #9

   design pressure has nothing to do with water tightness (see previous post) so sit up and take notes Im about to school you now that I understand better your question.

   Your house (any house anywhere) is engineered to withstand X amount of wind load. There are alot of factors that determine this and location is the prime factor to determine how much is needed. Wind speeds are highest at the coast and become progressively less the farther inland you are. Exposure to this wind is categorized by categories A-D. All of this information is taken into account when you apply for a permit to replace a garage door, door, roof, and windows. This is important because if the unit isnt designed to withstand the design pressure where it is installed you could have a failure. This failure could result in your home being damaged. the higher the dp the higher the pressure or wind force it is designed to withstand provided it is installed according to the test specs. (most are not). If you are concerned about watertightness replace the seals with bulb and or compression seals like on car doors, those are the best.

   Rob Pait- Cocoa Beach, eastern central fl

   hurricane rider

5. 
   oberon476 | Apr 18, 2007 03:49am | #10

   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 DP20 is tested for water infiltration at 3 psf (15% of 20psf) while a window with a DP40 is tested at 6psf (15% of 40).

   <!----> <!---->

   A window with a DP20 is rated to keep out rain when driven by 35mph winds and a window with a DP40 should be able to keep out rain when driven by 49mph winds...so water infiltration is DP related, and air infiltration is not, because the nature of air and water infiltration thru the window is different. 

   <!----> <!---->

   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).

   <!----> <!---->

   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 DP20 is rated to a pressure level equivalent to 89mph windspeed, but it is tested (for structural) at a pressure equivalent to 134mph.

    

   So, making things a tiny bit simpler, both BenM and the manufacturer are correct when discussing the window rating. 

    

   A window with a DP20 is rated to 88mph (structural) and 35mph (water infiltration)...less confusion?

    

    

   Edited 4/17/2007 8:54 pm ET by Oberon

6. 
   sledgehammer | Apr 18, 2007 04:04am | #11

   Clear enough.

   I'm sure this homeowner is going to be a litttle more then pissed at the builders selection and placement of this door.... after dropping 9 grand on it.

7. 
   Gene_Davis | Apr 18, 2007 06:35am | #12

   Tell us about the $9K door.  It may be that in the class of product the owner wanted, there is nothing at all available in the no-leak performance sought (or now needed).

   Patio doors, Andersen's Frenchwood hinged models for example, are designed, tested, and listed as having DP40-type performance, with some even higher.

   But that is not the case at all for entry doors.

8. 
   sledgehammer | Apr 18, 2007 02:44pm | #14

   Had anyone known this doors capabilities no one in their right mind would have ever put it where it is. Between the builder, acrhy or supplier... I'd bet someone is going to learn DP ratings the hard way.

9. 
   Gene_Davis | Apr 18, 2007 05:50pm | #15

   Please.  What is it?  There are many types of doors.

   Entry doors have simple weatherstripping, slab-mounted door sweeps that engage fixed or adjustable thresholds.  They can be wood, foamfilled steel, foamfilled fiberglass, or even hollow steel.  The locksets typically are of a different brand name than the door, and are field-installed.  Entry doors do not have high water penetration resistance.

   Are we talking about an entry door here?  Because if we are, the leaking really is not the fault of the door.

10. 
    sledgehammer | Apr 19, 2007 01:02am | #16

    It is a custom made arched top,double inswing french door with a 3 point locking system  provided buy the mfg. It is installed in an efis wall in a brand new 7 figure home.  For 9 grand you typically get alittle more then a foam filled steel.

    What I'm finding interesting is how little the average person in this industry really knows about pressure ratings other then the higher the number the better .... duh.

    It is not the doors fault. The mfg clearly states what the dp rating is and it is installed in the wrong location. Unfortunately either the supplier, builder or archy didn't understand DP ratings... but they will. I'm glad I started this thread because it has certainly been an eye opener for me at someone elses expensive expense.

     

11. 
    ChicagoMike | Apr 19, 2007 03:53am | #17

    I am surprised it passed the CO inpection. After hurricane Andrew National Building Codes were put in place specifically for all coastal areas. The closer to the coast, the higher the the required rating.

2. 
   WINSTALL | Apr 18, 2007 02:25pm | #13

   Have him/her buy an outswing door. It will tighten up as the wind gust and sustained winds gain strength. Ever wonder why all doors in Florida swing out ?????? Most of their hurricanes make a nor easter look like a gentle breeze.