During my service bureau career, I was involved in the production of transactional documents like bills, notices, and statements. We inserted every document into a window envelope. We had a warehouse full of them, printed with client logos and featuring windows of various sizes and locations. Window envelopes are still the norm for transactional documents, but today’s mailers have choices that weren’t practical just a few years ago. This article is all about envelopes, windows, document integrity, and variable data printing and how to choose the best solution for your unique situation.

Pros and Cons of Window Envelopes

The best aspect of window envelopes is the ability to verify the contents of the envelope after the machine has inserted the material. Printing a small 2D barcode or text in the address block allows cameras mounted at the end of the inserting line to scan through the window and compare document ID numbers against a file of expected mail pieces. If cameras detect a missing, out of sequence, or duplicate ID number, the inserting machine can stop, allowing operators to diagnose the problem.

Mail piece integrity checks are more important than ever. Once used only for transactional documents, accounting for every mail piece is now necessary on nearly all mailing jobs. Clients want to be sure all their mail went out. As marketers include more personalization in their campaigns, accuracy is vitally important. Clients are expecting applications like direct mail, which mailers used to process without precise integrity controls, to be subject to the same level of scrutiny as bank statements.

Window envelopes provide operations with a level of confidence that closed face (windowless) envelopes cannot. It’s comforting to see those addresses showing through the windows.

The window envelope approach has some drawbacks though. As I mentioned, our service bureau warehouse had many varieties on hand. Many envelopes looked almost identical. Though we enforced job set-up quality checks, humans can make mistakes. Simple errors like loading the wrong stock into the inserter or returning unused envelopes from last month’s run to the wrong pallet or carton in the warehouse could cause us to mail one client’s documents in another’s envelopes.

Some camera systems can catch this error by examining the return address area on each mail piece as it exits the equipment, ensuring the proper logos or return addresses appear on every one. Not everyone has this feature, so they rely on human eyes to ensure they’re using the proper envelopes throughout the run.

Some mailers avoid the mixed-envelope situation by using double window envelopes, allowing the return address on the inside document to show through the top window and the mailing address to appear in the lower window. This is a great approach if your shop intends to combine several small print jobs from different clients or applications into one large inserting job.

Two-window envelopes (or the alternative large single window varieties) impact document formats. Clients must reserve a substantial portion of the first page of their documents for address information and take care that no one can see confidential data like medical information or account numbers through the windows. You might recall a well-publicized case a few years ago when an insurer faced lawsuits and HIPAA infractions because of data showing through large envelope windows.

Our service bureau processed print-image files provided by our clients. Often our clients couldn’t change the way their documents were formatted. It wasn’t possible to align both address blocks with our standard double-window envelopes. In these cases, we had to insert documents into single-window envelopes pre-printed with the client’s logo and return address.

This brings us to another drawback of window envelopes. On some jobs, operators may have to reposition the inserting machine’s fold plates to make sure all mail pieces meet USPS regulations and the addresses show through the windows properly. This can be challenging when registration is tight, particularly for addresses with five or six lines that may be buried somewhere in the run. Folder adjustments, even those accomplished by automated means, take time. The machine isn’t running while adjustments are made, and operators must stop the equipment and check the lineup on the first few envelopes of the job. Productivity suffers. Obviously you can’t combine jobs, either, if they require different folds.

If your inserters accumulate pages before folding, page counts affect the alignment of addresses. The position of addresses printed on the first page of the document, relative to the window, will change for high page count documents.

Closed Face Envelopes

Mail piece integrity measures built into newer inserting equipment and add-on camera systems have made it less risky to insert documents into closed-face envelopes. This method uses inkjet heads attached to inserting machines to spray the recipient’s addresses and postal barcodes on the outside of a windowless envelope. The identity of each document is encoded in a barcode read from documents as a sheet feeder or cutter feeds pages into the inserter. The document ID number matches a data file that drives the inkjet printer at the end of the inserter. Sensors built into the inserting machines prevent the system from getting out of sync and printing the wrong address on the envelopes.

When document designers don’t have to contend with envelope windows, they are not constrained because of address blocks. This frees up document real estate and allows document designers to use the space to their advantage. They may be able to lower page counts because of the extra space, which reduces costs and shortens the time necessary for printing and inserting.

Because fold plates can remain in set positions, inserter operators won’t have to stop their machines as often or contend with unusual folds that result in uneven panel widths, which can contribute to jams. Closed face envelopes essentially separate the document layout from mail piece addressing requirements. Accumulating pages before folding won’t create “address creep” that affects deliverability on closed face envelopes like it can with window envelopes.

Closed-face envelopes can be pre-printed with the sender’s logo and return address or inserter-mounted inkjet heads can apply this information. Inkjet print quality for inserters has improved dramatically since the time I first investigated the technology. Advances in the ink-spraying equipment and the ink itself now allow organizations to print high quality full color content on the outside of envelopes at production speeds.

For a service bureau running jobs for multiple clients, closed-face envelopes present some interesting possibilities. You could buy plain white envelopes in large quantities, simplify inventory, and eliminate obsolescence. If the printing operation also employs a white paper workflow, you can merge jobs, print them in an optimal sequence for presorted mail, and improve productivity in both the printing and inserting steps.

If you can run larger inserting jobs, your operators can keep the machines running at top speed for longer periods of time. You’ll experience fewer stoppages during the day for machine change-over, material staging, logging, and reconciliation. You can transform hours of idle time into continuous production when you combine jobs.

Privacy concerns about revealing inappropriate information through envelope windows is obviously no longer an issue with closed-face envelopes.

Which Is Best?

Both window and closed-face envelopes have their strengths. The decision about which envelope style is best depends on your applications and work schedules. If you’re implementing a white paper workflow throughout your operation, switching to a closed-face solution is something worth considering.

With shrinking First-Class Mail volumes, combining jobs may be the only way to produce the mail economically. If address block placement varies on your present work, you must use envelopes with windows that will fit all cases while staying within USPS regulations (without allowing private information from showing). Or you can switch to windowless envelopes. Some analysis will be necessary to determine which solution is best for you.

Shops that insert the same documents all day are probably better off with window envelopes. They can design windows that meet the requirements for the jobs they run, set up their machines, and crank out the mail without having to worry much about address alignment and folder adjustments.

Envelope choice doesn’t need to be all or nothing. If you’ve got a substantial volume of documents that can be made to align in a standard one or two-window envelope, you can still combine those jobs. Use closed-face envelopes on the remaining jobs. There’s no reason you can’t do both.

Mike Porter at Print/Mail Consultants helps his clients meet the challenges they encounter in document operations and creates informational content for vendors and service providers in the document industry. Follow @PMCmike on Twitter, send a connection request on LinkedIn, or contact Mike directly at mporter@printmailconsultants.com.

This article originally appeared in the March/April, 2020 issue of Mailing Systems Technology.