You want to get your roofing client’s email address for a number of reasons.  The first is to communicate with them during the business operations phase.  This could be the product or service delivery.  If selling a product, you can provide email updates on your fulfillment process like order received, payment accepted and shipping confirmation.  If selling a service, you can provide an email update on making the appointment, notification a day before the appointment and send a follow-up email on completion of the service.  This are basic reasons to use email to communication with your client instead of calling them on the phone.

But, there are other reasons having a client’s email can help your business.  The first is keep in contact with them and continue to keep your business in their mind.  This might help if they need your service or product again or as a referral is someone they know might benefit from your product or service.  This communication could be in the form of a newsletter or some other timing email like a seasonal update.  The frequency should be enough to remind them of you but too much that they find it annoying or bothersome.  The frequency really depends on your marketing message.

Second reason is to send up-sell or follow-up offerings.  Hopefully your product or service has related products or regular needs.  If so, you can send that information along with maybe a discount if they purchase now.  If the product or service provides value to your roofing client, they won’t find it annoying because they are used to seeing communication from you.

On a final note, because the client already had a relationship with your, you are not violating the CAN-SPAM act.  But, you do need to the follow the guidelines for sending email including adding a way to unsubscribe from future emails.