Tag Archives: polycarbonate eave lights

Tyvek, Truss Attachments, and Polycarbonate Panels

Continuing to play catch-up with the Pole Barn Guru reader questions, Mike answers questions about adding Tyvek under wall steel, attaching trusses to header on sealed plans, and the use of polycarbonate panels for use on post frame building.

DEAR POLE BARN GURU: About to start the build of a 36 x 50 pole barn. Should I add a Tyvek or a “Block-IT” type material under the metal on the walls? I don’t know if I will ever finish the inside (maybe?) but where we live we get a ton of dust from farm fields etc. in the spring and winter before crops, and I am thinking that some type of material might help with drafts and dust. Seems quick and cheap to add now. Seems like everyone is squarely divided on yes/no. Thank you. MIKE in FREELAND

DEAR MIKE: Only reason to not have a Weather Resistant Barrier between your wall steel and framing would be if you were going to use closed cell spray foam insulation (in which case it should be applied directly to wall steel inside). It is so much easier to install now, than to wish you had done so after your building is completed.


DEAR POLE BARN GURU: My pole barn plans (architect designed & engineer stamped) show a double 2×12 header bolted into the notched top of the pole frame. Can the trusses sit directly on the top of the headers or should I put a typical double top plate on top of the headers (not shown on the plans). DAVE in PEYTON

Engineer sealed pole barnDEAR DAVE: You should erect your building exactly as shown on your engineer sealed plans, otherwise you have relieved your Engineer of Record of any responsibility for structural adequacy. Should you feel adding a top plate or plates to be necessary, please reach out to your engineer for clarification and a possible addendum to your plans.


DEAR POLE BARN GURU: Are some kind of translucent panels an option for pole barn roofing or siding? Similar to UPS Truck roof. Natural lighting. THOMAS in CHICAGO

post frame garageDEAR THOMAS: Polycarbonate panels may be used to provide natural lighting inside of non-insulated post frame buildings. In my opinion (as well as those of others) translucent panels should not be used in roof plane for a variety of reasons (https://www.hansenpolebuildings.com/2016/01/one-more-reason-to-not-use-skylights-in-steel-roofs/). They can be successfully used at top of one or both eave sidewalls or on triangles supported by end trusses.

Photos: https://hansenpolebuildings.com/uploads/polebarnquestions/cde6e9e0628de407178fc59261af7f68.jpeg


Eave Lights in Endwalls

Eave LightsPolycarbonate wall light panels are a very affordable way to get natural lighting into pole buildings which will not have finished interior walls. Most often (and most cost effective) is to install them at the tops of the eave sidewalls.

(For more reading on polycarbonate eave lights: https://www.hansenpolebuildings.com/blog/2011/09/polycarbonate-eavelights-light-up-my-life/)

There are some cases where it would work out better to polycarbonate panels on one or both peaked endwalls.

A caution – eave light panels should not be placed on endwalls below the bottom chord of the end truss, unless significant reinforcement is done to the endwall framing. Eave lights are not designed to be able to transfer shear loads and if placed below the truss, there is a strong possibility they will buckle, crack or fracture. Their failure could cause wind pressures within the building, which it was not designed for, resulting in total collapse.

How would reinforcement be accomplished? By adding appropriately sized steel strapping Xs to the corner bays of the endwall, such as Simpson Strong-Tie CS or CMST: https://www.strongtie.com/products/connectors/cs-cmst.asp

The challenges of using strapping is it must be sized appropriately for the shear loads being transferred to the end of the building, and a significant length of strap must be wrapped around the column at each end, with lots of nails into the column.

So, under what circumstances might “end lights” be appropriate?

When the building is placed so the wall which receives the greatest amount of sunlight is an end. Think of a building placed with eave sidewalls amongst trees, or other buildings which would cause shade.

Another case would be when a side shed or sheds would cause sidewall eave lights to be in the dark.

When adding end lights, the top of the endwall steel panels should be attached to the bottom of the truss, or end truss bottom chord siding backing, with diaphragm screws on each side of every high rib. Z flashing should be placed above the wall steel, then the light panels can be installed with screws every nine inches on center across all horizontal framing.

Keep in mind, any end truss members will “show” through the panels, even though they are most often ordered as opaque white. If end lights are installed below the truss bottom chord and shearwalls reinforced with steel strapping, this strapping will most likely show through the end lights, as well as any wood framing.

With all these considerations, my best advice is always to design a building in such a way the polycarbonate panels for lighting can be placed in sidewalls.

Installing Eave Lights

Tips for Installing Eave Light Panels

For those who are not insulating the sidewalls of their pole buildings and are looking for a low cost alternative to windows for getting daylighting into their buildings – polycarbonate eave lights might very well be the answer.

I’ve written about them in the past (see: https://www.hansenpolebuildings.com/blog/2011/09/polycarbonate-eavelights-light-up-my-life/), so I won’t expound so much upon their benefits, as much as keeping those who install them from being disappointed.

eave lightsAs one might expect – steel panels and polycarbonate eave lights expand and contract at different rates. Hence the use of a “z” flashing between the two in sidewall installations (or at least for those who, in my humble opinion, do it right).

The natural inclination is to place the panels into what “feels” like a tight overlap.

While us listeners of what is now “oldies” music, remember “Hooked on a Feeling” as the 1974 Billboard #1 hit by the Swedish cover band “Blue Swede”, being hooked on a feeling when installing polycarbonate panels can get you in trouble.

Shown in the photo is the 12th of the 36 inch net coverage panels on the sidewall of a 36 foot long building. The last panel falls about four inches shy of the corner of the building – not the ideal landing point.

In order to make sure adequate coverage of the panels occurs (as well as not needing more materials), the best solution is to measure the distance between overlaps of each successive panel. Any answer other than the 36 inch width of the panel is the incorrect one.

In this case, the eave lights should be screwed down first closest to the previously installed panel, then “pulled” until the panel’s full three foot wide coverage is achieved. If the measure is greater than the three feet, push the leading edge of the panel in the direction of the first installed screw until the three foot point is reached, then place the screws in the proper position closest to the leading edge.

For those trivia buffs – “Hooked on a Feeling” was originally recorded in 1968 by B.J. Thomas, but the famous “ooga-chaka ooga-chaka” background can be credited to British pop eccentric Jonathan King!

Polycarbonate versus Acrylic Eave Lights

Once again, we do the research, so you don’t have to!

My loyal readers will recognize I have researched some things which maybe no one will ever care about. From my perspective – if it makes a difference to even one person, then it was worth the work.

eave lightsRecently one of our clients asked for a comparison between a Hansen Pole Building, and building produced by another provider. In doing the research to be able to give the client a qualified answer, I did come across a product which I was not familiar with – Acrylit®. Acrylit is a panel which is manufactured with 100% Acrylic resin with Gel Coat protection on both sides. Acrylit panels can be used for eave and ridge lights – which allow for natural light to enter pole buildings which do not have interior finished walls or ceilings.

For more information on eave lights: https://www.hansenpolebuildings.com/blog/2013/07/eave-light/

Hansen Pole Buildings provides CoverLite® Polycarbonate panels for use as eave lights. These panels offer a high degree of light transmittance due to its high optical properties, with up to 90% light transmission. They are economical and light weight, yet 10 times stronger than acrylic and 200 times stronger than glass! CoverLite comes with a full 10 year warranty against yellowing and a five year warranty against breakage caused by hail.

In discussions with AmeriLux (the manufacturer of CoverLite), it was found Coverlite Solar Grade Polycarbonate Corrugated will not undergo a loss in light transmission in excess of 15 (fifteen) percent in comparison with the original value when tested in accordance with ASTM D 1003 (95); will not undergo a change in excess of 15 (fifteen) delta in comparison with the original value when tested in accordance with ASTM E 313-73.

I actually read the ASTM standards referenced, and you can read ASTM D 1003 here: https://www.astm.org/Standards/D1003.htm

ASTM E313-73 Is the “Standard Test Method for Indexes of Whiteness and Yellowness of Near-White, Opaque Materials”

What really caught my attention was: Acrylic will burn/melt rather than self-extinguish like polycarbonate would.

There are lots of fires in pole buildings, adding a product which will contribute to a burn does not sound like a prudent choice to me. Add this to polycarbonate being ten times as strong as acrylic panels, and we’ve got a hands down winner!

Oh, and did I mention acrylic is more expensive? For those who care only about cost, it’s a no brainer.


A request we receive frequently is for skylights to be installed in the steel covered roofs of our pole buildings.

My first thoughts go back to a building I worked inside of over the winter of 1980-81. About 20 years old, the building had a steel roof with numerous fiberglass (actually Fiberglass Reinforced Plastic or FRP) panels in the roof. These panels were designed and placed with the intent of allowing natural light into this very large building. The operative word here being “were”.

FRP panels are strong mold-resistant sheets. Over time the glazed pigmented seal applied during the manufacturing process can crack causing the structural breakdown of fiberglass resin by weathering. In the case of this particular building, the skylights had deteriorated to a less than lovely yellow color, allowing very little light transmission. Lateral loads being transferred through the roof from wind had elongated the holes around the screws, causing numerous roof leaks.

Brittleness over time is another issue with FRP. At the first truss manufacturing plant I owned, we constructed a new building in 1982, with FRP panels at the top of the south facing sidewall. The idea was to be able to gain natural lighting. Within a matter of just a few years, the panels had yellowed and become brittle. Local kids, out for “fun” were throwing rocks through the panels!

Available technologies have improved. For use in pole buildings, most instances where FRP panels would have been used, the work is now being done by polycarbonates.

Polycarbonate panels are designed specifically to match up to the metal panel profile. With a high performance glazing which stands up to punishing exterior applications, Polycarbonate Panels offer multiple advantages over traditional FRP panels: up to 20 times greater impact resistance, the highest light transmission rates, the lowest yellowing index, the highest load rating, and the highest resistance to wind uplift-outstanding properties confirmed in accredited laboratory testing and in installations worldwide since 1984. Polycarbonate panels are virtually unbreakable, they self-extinguish if exposed to flame, are hail resistant and are Underwriters Laboratory (UL) 580 Class 90 recognized.

Polycarbonate roof panels are normally used as in-plane translucent panels and are used with steel panels. Instead, we recommend these skylights be used in the walls as eave lights to allow light into the building to prevent anyone from walking on these panels.

If you are really planning on using polycarbonate roof panels, then you cannot insulate the roof in these areas, or you will block all the light. Roof areas without a good vapor barrier, which would be provided by properly installed insulation, are prone to condensation issues as well. You’ll also have to take some precautions about thermal movement. Polycarbonate panels do expand and contract much more than steel panels and they are much weaker and deflect more.

We’ve had an engineer perform full scale testing of steel panels similar to what is used on your new Hansen Pole Building (our tests were performed using thinner 30 gauge steel). These tests resulted in shear values for these panels being published in the National Frame Builders Association (NFBA) Post-Frame Building Design Manual. With a minimum allowable shear strength of 110 pounds per lineal foot, this steel is identical in strength to 7/16” oriented strand board (osb) installed in an unblocked diaphragm (no blocking at the seams between the sheets of osb).

Properly installed steel roofing, has the shear strength to be able to transfer loads induced by wind or seismic forces across the roof, through the building endwalls, to the ground. Herein lies the issue with light panels (either FRP or Polycarbonate).  They have no shear strength. In adding light panels, the structural integrity of the roof could be compromised. Under lateral loads, the panels could fracture or buckle, or the building frame itself could be overstressed.

There ARE some solutions as well as alternatives. Least costly would be to utilize light panels at the top of one or both sidewalls, or in the triangle area of one or both gable ends. Another affordable option would be to use a translucent ridge cap.

If light panels absolutely must be installed in the plane of the roof as skylights, the area can be reinforced by using steel strapping as an X from truss to truss on top of the roof purlins. This X will be seen through the light panels in the roof.  Aesthetics of the roof may be a consideration, especially with steeper sloped roofs where it is easily seen from the ground.  Also, while this solution adds to the cost of materials, as well as slows installation, it does afford a solution.