The Building Envelope

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Author of "Engineer to Entrepreneur: Success Strategies to Manage Your Career and Start Your Own Firm", President and Founder of DLG Engineering, Inc., avid photographer and over 20 years of work experience in the forensic investigation, design, analysis, consulting and inspections of residential, commercial and retail building envelope components. 

Friday, September 15, 2017

Structural PSA #6: Live in a Condo?

If you live in a condo building where you are responsible for your exterior windows and doors, make sure to determine what type of demising wall (wall in common with the units next to you and the hallways) you have. The problem with protecting a condo unit, individually from your neighbor and the building as a whole, is that typically the demising walls and entrance doors are designed as interior walls & doors and are not adequate to sustain strong forces. That is, unless your demising walls (such as in some townhouses) are a structural fire wall or shear wall. Therefore, if you protect your unit with impact windows and your neighbor does not, more than likely your demising wall in common with them will fail, as well, should they lose a window or door in the storm. The interior walls are designed to support only 5 pounds per sq. ft. whereas wind forces for a condo can be in the order of 50 to 130 pounds per sq. ft. If your neighbors windows fail that would introduce large positive pressure, debris and water which will affect everyone on your floor and most likely introduce water to the units below. Should this happen, the safest place in the building would be the stairwell which is typically solid concrete or masonry all around. I would not worry about the roof, per se, as flat roofs in condos are typically of reinforced concrete. Condo buildings need to design for such occurrences holistically and protect the entire envelope. Do not think just because your unit is protected with impact windows and doors, that you are safe during a strong storm.

Thursday, September 14, 2017

Structural PSA's Before, During and After Hurricane IRMA

Structural PSA #1:

Products ARE NOT designed for wind speeds, that is a commonly repeated false statement. Products are designed for pressure. Buildings are designed with wind speed as one of the factors of their design pressure. Design pressure is based on wind speed (squared), roof type, height above grade, surrounding terrain, etc. Then, a factor is placed on the design load based on building essential value to recovery or shelter. All of these factors affect the pressure that a storm imposes on a structure or that a product is designed for. A single family residence products are designed to sustain forces in the order of 40 pounds per sq. ft. A high rise products are designed in the order of 85 pounds per sq. ft. In summary...Don't be fooled by people who tell or sell you that a window can sustain X mph winds, that is impossible to tell. Windows can sustain pressures. The same wind speed can produce radically different pressures. You need to know your unique design pressure before you buy your windows.



Structural PSA #2:

The impact force is a different story. Products are designed to sustain two different types of missile impacts based on height above grade (over 30 ft or below 30 ft). The design standard for products below 30 ft (large missile) is a 9 ft long, 9 pound 2x4 shot from a laser guided cannon at 50 ft per second at three locations. Above 30 ft, the design criteria is ball bearings, 30, shot at the product in three groups of 10. Products must sustain theses loads and then are subjected in the lab to 9000 wind load cycles at the design pressure, 4500 cycles in the positive direction and 4500 cycles in the negative direction. Our products are VERY STRONG if installed properly.



Structural PSA #3:

Impact windows versus shutters. It is a matter of cost vs convenience. Impact windows will protect you equally, they are both designed for the same criteria/pressure. The difference is shutters can be opened and removed and than reused. Impact windows provide you the convenience of not having to board up or put up your shutters but broken impact windows must be replaced. If you can afford the cost and prefer the convenience, impact windows are the option for you. If you cannot afford the cost to replace your windows shutters are your best option.



Structural PSA #4:

We are all told that the state of Florida has one uniform building code as a result of lessons learned from Andrew. However, while on paper we all follow one code BOOK, the actual specifications and requirements for hurricane design in the code are in fact separated into two distinct sections. The general code and the High Velocity Impact Zone (HVHZ) which by definition includes Miami-Dade and Broward counties ONLY. The HVHZ is the stricter code. The reason for that is....(too political and lengthy to discuss on FB)



Structural PSA #5:

PLEASE do not be fooled by IRMA's effects on Florida (Exception: The Florida Keys). Do not say your house "Survived IRMA therefore it can survive anything" when another storm threatens us in the future, and it WILL. Certainly there is a lot of suffering and it is not my intent to minimize it (loss of power, downed trees, some structural damage and lots of water infiltration) IN MY OPINION, this was nothing but a strong tropical storm event for us in Miami-Dade and Broward counties and a CAT 2 for North Florida. Nowhere near a "code testing" event. For the true impact of IRMA you only need to look at the Caribbean and the Florida Keys. I made a very controversial post about a week away from what was expected to be a monstrous category 5 hurricane with winds of 185 mph that I immediately took down for fear of panic. I advised not to try and ride out IRMA at it's present wind speeds. I myself considered leaving until the winds lowered to below code level speeds. What I should have written was to not try and ride out IRMA (at 185 mph) in a single family residence and instead seek a proper shelter. Have a plan, in the future, for a code level event, in my opinion 150 mph or less (we design for 175 mph, but my faith in plans review, installations and inspections of very well designed and tested products is very poor based on experience) and then have a plan for the monster storm 151 mph plus. As I posted previously, the wind speed causes the pressure to exponentially increase or decrease with each mph which is the true measure of a building or product's strength. In fact, I am VERY concerned that with such a minimal wind event many are praising our preparedness and our ability to survive a code level event especially considering the enormous loss of power after tropical storm force winds.

I AM CONCERNED THAT WE, AS A COMMUNITY, WILL HAVE A FALSE SENSE OF SECURITY AFTER THIS.

WE HAVE A LOT MORE TO DO FOLKS TO BE PREPARED FOR A POWERFUL STORM SUCH AS IRMA...AT IT'S PEAK WINDS.

WE DODGED A BULLET.

Tuesday, February 25, 2014

Top 10 Reasons to Hire a Building Envelope Consultant

Valuable information for developers, architects and engineers working in hurricane prone states.

Click on the title to be directed to the presentation.


Saturday, June 30, 2012

Hurricane Mitigation: Have We Learned From Our Past?

It has been close to twenty years since Hurricane Andrew struck South Florida.  Much time, effort and money has gone into investigating the devastation and attempting to make changes to minimize the damage in the future.  Have we learned enough to make us safer?  Have we implemented sufficient changes based on what we have learned?  Are those changes being properly enforced?

The answer to those questions is not a simple one and it will vary from municipaliy to municipality and from region to region.

If you focus on the entire State of Florida, the answer would have to be no to all three questions.  If you focus on South Florida, generally speaking, especially Miami-Dade and Broward Counties, the answer would be yes to all three questions. 

The discrepancy in the answers to the above questions is only natural since you have to have experienced the devastation first hand in order to properly appreciate the urgency and desire to change.  There is a constant and intense struggle between South Florida and the rest of the state with respect to implementing and enforcing what we have learned.  South Florida has implemented a safe code whereas the rest of the state has not.  South Florida has implemented strict product control whereas the rest of the state is attempting to weaken that control. 

If we have this intense struggle in the State where hurricane codes are the strictest and most advanced, and there is still tremedous lack of implementation and enforcement, how do you think the rest of the hurricane prone regions stand as far as hurricane preparedness??

Not good, I would have to guess...not good!

Wednesday, October 5, 2011

Building Envelopes Critical To Nation's Infrastructure

It is critical that we raise awareness on the status of our nation's building envelopes and their importance to the protection of our nation's infrastructure.  Please read the attached article as well as the referenced white paper with recommendation to congress.

Rick De La Guardia

Friday, August 26, 2011

Are our Building Envelopes Ready for a Powerful Hurricane?

As an experienced building envelope consultant specializing in hazard mitigation design, I feel compelled to pass along some advice to those not familar or aware of the possible dangers and aftermath of a powerful (Category 3 or above) hurricane.  I do not want to focus on preparedness since there are many sources available to the public in today's media speaking to that topic.  I want to focus primarily and uniquely on what I consider to be issues in how we structurally address the building envelope.  After nearly 18 years in the business of design, inspection, analysis and consultation in this field, I can say, without a doubt, that we have alot to learn in order to bring our building envelopes to an acceptable level of protection.  Even in the state of Florida home to the country's strictest building codes with respect to hurricane mitigation there is much work to be done.  I have made it one of my firms highest priorites to raise awareness and bring attention to these issues.  Not enough emphasis has been placed on securing the building envelopes in the other coastal states that are more and more being threatened.  I am writing this blog now because of the heightened awareness and potential test to our nations northeast building envelopes.  My issues of concern are:

1.  The afffects from wind load are being considered in most cases but the affects of windborne debris have not been given due attention from our northeastern neighbors.

2.  Installation of windows, doors and storefronts are being installed in substrates that are not adequate to transfer those forces to the main building structure...such as improperly attached wood bucks, inadequately designed metal stud framing, excessive shimming of anchors.

3.  Envelope products are being sold and installed without proper engineering and testing.

4.  Products that are properly engineered and tested are being installed improperly and with disregard to the testing and design limitations.

5.  The impact resitant glass types on installed products are sometimes being substituted with cheaper, weaker glass.

6.  Many municipalities approve building envelope shop drawings and calculations without proper review just because it contains an engineers seal.  You would be surprised how many signed and sealed shop drawings and calculations I have reviewed,, that have been prepared by seasoned engineers in which I have found gross misinterpretations or even disregard for the code.

7.  There exists a lack of awareness from architects and structural engineers on the intracacies of designing the building envelope and on the product approval process.

8.  There is a misconception that the glass on impact resistant products will not break during a storm.  In fact, the glass might very well break but if installed properly will not separate from the frame.

9.  There is a serious lack of knowledge with many of todays building inspectors regarding interpreting and enforcing approved shop drawings.

10.  There is much work needed to bring shop drawings up to par with being an adequate representation of the product approvals and the specialty engineers design intent.

11.  There is rampant fraud and lack of oversight in the hurricane mitigation inspection process performed for the insurance companies.

I could seriously go on and on but will stop by saying that it will not be until an Andrew or like storm hits a major metropolitan area that these issues will start being addressed.  Let's hope and pray that the time is not now for the sake of our northeastern neighbors.

The answer to the question, in my opinion, is.....NO!



Saturday, December 19, 2009

Windows & Doors

Miami-Dade and Broward County are located in what is referred to as the "High Velocity Hurrricane Zone" in the Florida Building Code.

This means that these two Counties have stricter design requirements then the rest of the state.

The minimum (hurricane) wind speed that one must design for is 146 mph in Miami-Dade and 140 mph in Broward. This wind speed is the same for all buildings and not to be confused with the design wind pressure which varies from building to building.

In order for a manufacturer of windows and doors to be able to sell their product to the public it must comply with the above Code requirements, be tested and receive a product approval or Notice of Acceptance (NOA) from Miami-Dade county.

Just because a product has an NOA does not mean that it can be used everywhere. The product comes rated at a certain wind pressure that must be equal or greater than what the architect or engineer has determined is the design wind pressure for your home.

The tip here is: MAKE SURE THAT, BEFORE YOU BUY WINDOWS OR DOORS, YOU ASK TO SEE A COPY OF THE NOA AND CHECK THAT THE RATED WIND PRESSURE FOR THE WINDOW IS SUFFICIENT TO MEET THE DESIGN WIND PRESSURE FOR YOUR HOME.

Forensic Investigation of Glazing

The steps in determining what went wrong is to:

1. Determine the design criteria (applicable code).
2. Identify the specifications for the project provided by Architect or Engineer.
3. Confirm project design wind loads.
4. Review shop drawings & calc's for compliance w/ code & project specs.
5. Review product NOA's or State approval documents.
6. Perform inspection to confirm product and installation.

Things to look for:

Design:

1. Proper wind load factors and tributary areas.
2. Adherence to limitations of product NOA's or State approvals.
3. Allowable stresses of steel and aluminum.
4. Allowable load of anchors including (edge, spacing & cantilever reductions)

Installation:

1. Check product for compliance with NOA's or State approvals.
2. Check glass type & interlayer.
3. Check anchor types and shimming including substrate conditions.

Thursday, December 10, 2009

Glass Types for Building Envelope Products

There are typically four different glass types used in glazing products: From weakest to strongest they are: Annealed, Heat Strengthened, Tempered and Laminated.

1. Annealed glass is your basic non-impact glass type. It is used in applications where the required wind load is not so high and safety requirements are not a concern. When annealed glass breaks, it breaks in sharp chards.

2. Heat Strengthened glass is also a non-impact glass. It undergoes a "heat treatment" that increases it's strength to twice that of annealed glass. It is used in similar applications to annealed glass but where the required wind loads are much higher. When heat strengthened glass breaks, it also breaks in chards.

3. Tempered glass is your basic impact glass. It undergoes a more aggressive "treatment" that increases it's strength to four times that of annealed glass. It is used in "small missile" impact applications typically installed 30 feet or higher above ground and in safeguard applications. When tempered glass breaks, it breaks into very small cubes.

4. Laminated glass is your typical impact glass. It is a combination of two (usually) of the three previously mentioned glass types that are "laminated" together with an interlayer between them. It is typically used in "large missile" impact applications installed up to 30 feet above ground. When laminated glass breaks, it breaks based on it's glass type make-up but is held in place by the interlayer...similar to a car's windshield.

Designing in Florida

Issues to consider when designing a project in Florida.

1. What County is it in? The Florida Building code, 2007 edition identifies Miami-Dade & Broward Counties as being in the High Velocity Hurricane Zone therefore subject to stricter code compliance.

2. Is the County in the Wind Borne debris region? This encompasses all areas where the design wind speed is 120 mph or greater OR 110 mph if the design area is within 1 mile of the coast. The wind borne debris region requires impact protection or impact resistant products.

3. The glazing product most have either a State of Florida OR a Miami-Dade County product approval.

4. Local ordinances: Some municipalities require compliance above and beyond the Florida Building Code requirements. Check with the local building department prior to design. Example Coral Gables (Miami-Dade County) does not allow light gage framing as exterior walls. Some coastal municipalities require turtle friendly glass specs to be used to prevent disorientation of turtle hatchlings.

5. Inspections: Some municipalities require a special inspector form to be provided prior to issuing a permit.

These are just a few of the unique requirements of designing a project in Florida.

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