Energy modeling software has become quite important in the last decade, mostly because of the LEED credits involved with energy usage (and the need to reduce long-term energy use because of costs). Energy use estimations in these cases have tended to be inaccurate, for as of yet unknown reasons. The USGBC is now mandating energy use reporting periods in order to track down the problems, and I have no doubt that eventually the problems will be found.
In the meantime, what are building designers to do? A good idea is to use any results from energy modeling as a guide rather than a gospel.
Energy modeling is still a very useful process. If for nothing else it makes you think long and hard about decisions that were once hidden behind a veil of complexity. Lighting issues matter, HVAC issues matter, renewable energy sources matter. With a little bit of attention and ingenuity, our buildings can start saving money and emissions from the first day of operation.
Software that allows one to calculate the true effects of every project decision is somewhere in the region of non-existent or too expensive. But we have great reason to celebrate, because energy modeling is about to become widely available and much more accurate.
The US Dept. of Energy has been steadily working on their EnergyPlus program for several years. This program is the calculating engine behind most of the software packages today. It incorporates everything that people know about heat transfer and energy usage. The one thing missing is a Graphical User Interface. Previously there was only one option if you needed a GUI – you can purchase a commercial package such as offered by Bentley, Autodesk, or IES.
If you can can’t afford this, or are just looking to play around with some fun freeware programs then I strongly suggest everyone investigate the new SketchUp plugin IES-VE Ware. With this setup, you can draw a design in SketchUp and do limited energy analyses with the plugin. It won’t be enough to estimate your monthly bill, and certainly nowhere near the sophistication needed to qualify for LEED points, but it’s a good start. (see the plugins at SketchUp’s own site)
It’s only a rumor, but I have heard that ASHRAE believes a new user interface for the EnergyPlus engine will become available within the next year or two. This would usher in a new era of energy modeling of the people, by the people, and for the people! Keep your fingers crossed, we may get lucky.
Of special note to anyone who been working with facade connections in steel buildings is two documents from AISC. The first is their “Design Guide 22: Facade Attachments to Steel-Framed Buildings” and the other is a recent article in MSC: “Steel Framing & Building Envelopes”.
The Design Guide 22 is free to AISC members (~$60 otherwise) and is probably one of their best. It has a great amount of information about spandrel beams, connections, facade issues, and even backs it up with some FEA work.
The MSC article “Steel Framing & Building Envelopes” by James A. D’Aloisio, PE, SECB, LEED AP should be considered as an addendum to the design guide, specifically dealing with the issues of thermal bridging and building envelope thermal performance. Basically, if an engineer applies the suggestions from DG22 without considering thermal bridging effects, then the R-value of the wall assembly could be halved (!).
D’Aloisio’s has published some interesting details he is experimenting with. His recommendation is to always use a thermal break, and he shows a Fiberglass-Reinforced Plastic shim plate to isolate steel lintels and hangers from the exterior environment. As he points out, many LEED NC buildings are not meeting their expected performance levels. The reason may be because of conventional details used by the construction industry.
As many structural engineers can tell you, streamlining the design and construction process is a great way to keep cost under control. With that in mind, here is another link to an engineer’s website: Accelerated Bridge Construction.
It has a pretty good blogroll of interesting bridge websites for those who are interested, and also some posts of normal events through the eyes of an engineer.
I’ve been quite busy since my last post. In fact, I found time to:
- build a patio
- repair some leaking pipes
- pull out the motorcycle
- general house maintenance
It’s been great with the perfect weather we’ve been having. No complaints whatsoever.
I did come across a new blog about bridge building in the UK. Thought it was good stuff, wanted to share it with everyone. It’s also added to my sidebar. I strongly recommend everyone view the insightful posts about criticism in the engineering field.
When undertaking the renovation of an historic masonry building, there are two major issues that must be dealt with early in the design phase – what to do about thermal insulation and old windows (I’ll deal with windows on another day). If the building was built before the 1950′s, it is likely that the building was not designed to take advantage of our current HVAC technology, so don’t expect to put in a simple set of ducts and a furnace and move in. As I have been learning more about renovating masonry structures, I have realized it’s much more complicated than that.
The first source of information for any historic project is to consult the Secretary of Interior’s Standards for the Treatment of Historic Properties
and the preservation briefs
. The standards represent the consensus opinion of historic preservationists and will serve as a guideline for most phases of the project. Some of the requirements may sound expensive or unnecessary, but I strongly suggest following them. If anyone chooses to disregard this advice, please consider doing a lot of research into alternate options before making a final decision.
Keeping heat in your building requires a thermal envelope. When it comes to thermal insulation, brick is a disaster. Don’t let anyone lie to you, this material is a horrible insulator. Sometimes you will read about the benefits of high mass, a mass factor (or M factor), adjusted insulation value, or similar theories. Some of these claims are true under specific conditions, but not in a cold climate. The important thing to understand is that the R value of historic masonry is not high, thus heat and cold will transfer readily through the walls. Masonry walls are typically rated about R = 0.15/in, so a 16″ thick wall has an R = 2.5. Minimum standards for a new building in the midwest are approximately R = 16. This means a modern building has a wall that transmits heat 8x less than a typical historic masonry wall.
This assumes that the R = 2.5 value is accurate, while in reality it may have an actual R = 1.5 or less, there is just so much uncertainty that it is wise to be conservative in your calculations. Basically, the old brick wall is going to need some help in the form of additional insulation. It is possible to add insulation on the exterior or interior, with the interior being much more common because who wants to cover up the facade of an historic building? At this point, we must introduce the next complication: moisture.
Insulating a brick wall by just throwing up some fiberglass batts or foam board puts the brick wall in a bad situation. The wall is the same temperature as the exterior weather, but is exposed to interior air. This will cause condensation on the interior surface, just like the water that puddles around a cold glass during a humid summer day. A typical building has an interior Relative Humidity level of 30% or so. This is a lot of moisture (a lot!), and moisture/water can easily destroy an historic building. If the walls are cold and exposed to the humid interior air, the wall will generate a nearly unlimited amount of water over the life of the building.
Wet insulation has an R value of nil, and wet wood stud walls is a recipe for mold growth. Attempts have been made to reduce the exposure of walls by way of vapor barriers, but this usually just seals in the moisture. Trying to reduce the problem by incorporating vents usually defeats the purpose of insulating in the first place.
As of right now, there is no easy, cheap way to insulate. Large, expensive renovations should consult a specialist when dealing with this scenario, because conventional construction methods will not work. Smaller scale projects should probably base their solution on proven methods, and luckily we now have some great examples. So here are the success stories:
The best one I have seen yet is a renovation done for Harvard University, the Blackstone Office building by Bruner Cott (certified LEED Platinum).
Another source of information is the renovation of the Portland Armory building. This was renovated for the new home of a theater, and they faced many of the same issues as a typical masonry project as well as some special ones because of the large interior spaces. Also certified LEED Platinum.
Finally, the renovation of the Lofts St. James in Montreal. As with this project, any successful strategy involves finding a way to control heat flow, moisture flow, and air flow. Every project is unique, especially when dealing with existing buildings, but there are always ways to get across the finish line.
Heads up for all the building designers out there… Bracing is Beautiful!
There are very few building systems as cheap and efficient as braced frames. Allowing your engineers to put just a few braces in the building will make them a very happy person. You’ll see a lower cost per sq. ft of building, use less material, and make a green statement. Moment frames open up the floor areas, but you sacrifice a lot of room for the deeper beams, bigger columns, and tricky connections.
The most important reason to consider bracing is that people love seeing structure expressed in their buildings. It worked for the Hancock Center in Chicago, and it can work for you! There are buildings and architectural styles that it won’t work for, but you can hide the braces pretty easily.
There are many flavors of bracing. Concentric, eccentric, chevron, knee, buckling restrained braces, multi-story bracing, etc. Just put those terms into an image search and you’ll see a world of options waiting for you.
If you are concerned about exposed steel members (fire resistance, corrosion, vandalism) then you may want to coordinate with a specialist during your initial design. If appearance is a concern, then I strongly recommend you consider some of the newer imported components available. For smaller loads, a pin-connected rod from StaLok will work, whereas for a Cast Connex bracing component can handle even large bracing forces seen in high seismic areas.
We all want to do our part to help the owners get the building they want – at a reasonable cost with great performance. I think recommending a bracing system is a great way for engineers to add value to the project, without the high initial cost of shearwalls or moment frames.
For owners/engineers/architects looking to estimate how much it would cost to do an actual seismic renovation or upgrade to an existing building, see this online calculator.
You have a few options to get an answer, but I recommend using the detailed option and form entry. When I go through the exercise using my own building, I get ~$82 per sq. ft. which works out to a total cost of $500k for a complete seismic retrofit. I promise to get around to that as soon as I can…
Note that the choices you make can have large consequences on the overall cost. When I choose a lower the lowest goal of “risk reduction” and limit other anticipated work then the cost drops to half of the original $82/sq.ft.
The methodology is based on a database of retrofit projects. It knows how much those projects ended up costing, so it can compare the variables chosen for your project against the database and come up with an accurate market driven answer. Pretty nifty. Now you can tell your clients that you have a pretty good idea how much the work will cost. Of course, you might want to really investigate the options and help menus before you submit any numbers from it. And don’t forget to convert the answer to today’s values, because the cost it gives you is in terms of 2002 dollar values.
Everyone who is an architect, engineer, contractor, or just likes tall buildings ought to know that CTBUH has just put the 2008 World Congress (held in Dubai) videos online.
I also want to extend my congratulations to CTBUH for hosting a successful World Congress and sharing all the information freely. You may have ruined every Friday night for the next few months by putting these videos up, but I’m very appreciative.
For anyone interested in learning a lot in a short time, I couldn’t recommend anything better than the AISC steel webinars. Kick ass engineering. It is a great format – recorded lectures by industry experts especially meant for a young engineering audience. There are 4 available and each is 6 hours long.
Screenshot from AISC Webinar
There are a few interesting things you should know about these. First, these were originally just normal seminars that the experts presented around the country. There was no intention of webcasting them. However, people rated them so highly that a clever person at AISC decided that people could really benefit from them. And so the experts came back for an encore presentation that was recorded. That means they had plenty of practice and time to work out all the bugs. The final result is quite good, and well worth your time. I’ve seen all them thru, some more than once. Don’t plan on doing them all in one week, your head will explode.
MSC is another great resource freely available to AISC members
When you’re done watching, try to explore some of the other resources that AISC makes freely available to all its members. There is the Modern Steel magazine, Boxed Lunches, the Engineering Journal (and archives), the FAQ’s, and the “Ask AISC” where you can actually pose a question to the steel experts there. That last part is generally a good resource, but you get what you pay for sometimes. There really is no other construction design organization as well organized and offering you more opportunities to learn than AISC, and you should be taking advantage of it. Well, maybe ASCE but I haven’t seen them post any free webinars – hint hint.
For those who have more than a passing interest in Earthquake research happening in the Eastern US (i.e. not California) we have plenty of resources.
First off is the USGS – US Geological Survey. They are the clearinghouse for all things dealing with rock, soil, faults, etc. You will still need a qualified soils engineer to determine site classification, but their soil explorer program can sometimes provide you with some interesting advance information. If a previous soil boring was reported to the USGS, and it showed bedrock at 5 feet, you can make an assumption that soil classification will be favorable.
Next up is the Mid-America Earthquake Center. This is a group of researchers dedicated to mitigating the possible problems that a large earthquake in the Central US might cause. They especially focus on the many historic buildings (unreinforced masonry) and even modern buildings that were built before awareness of the seismic risk in the area. The worst historic earthquake (magnitude, not damage) was in this area, so there is a good reason to be concerned. A good source for graduate funding, too.
Then there is the Central US Earthquake Consortium. This was started by FEMA to handle the human aspects of Earthquakes. So this doesn’t deal so much with research, but is all about the government response and disaster preparedness/awareness. It’s all about coordination. A good resource nonetheless.
CERI is another great resource. They have a lot of independent information, as well as links for teachers and students. Was able to find a waveform taken from a Missouri station of the earthquake here. These people also have graduate funding programs available for students.
More general information about midwest earthquake risks:
New Madrid Seismic Zone
Wabash Valley Seismic Zone
I believe the most important thing when anyone asks an engineer about these topics, or related disaster topics such as building collapses, hurricanes, etc. is to refer them to the appropriate spokespersons for our industry. Alternatively, read up or interview someone from one the groups in advance if you know that a newspaper or media outlet will be contacting you for a response. It is essential that the public knows the most recent information and that we present the consensus opinion to the media. Don’t take the fools way out and use the publicity to invent your own conspiracy theory.
update – 5/30/08
How could I forget about NEHRP? The National Earthquake Hazards Reduction Program is another government entity dedicated to reducing earthquake losses in the US. This is a great resource for any structural engineer dealing with seismic design. It is especially relevant for older buildings that are being updated or going through seismic hazard mitigation. The methodologies used are somewhat different from the IBC and UBC code provisions for new buildings and you won’t always get a “yes/no” answer on a design. They have also posted a recent newsletter describing the efforts to develop a consensus based document for performance based design of seismic resistant structures. See the interim FEMA 461 document here.