I’d like to point out that a Professional Engineer’s standard of care typically includes a site visit to assess field conditions and get an overall understanding of the structure. This can obviously not be accomplished through the internet. The information provided here is meant for planning purposes only (general sizing and budgeting) and is based on the information provided by you. All loading cases considered are for vertical loads only, no lateral analysis has been completed. The information should be verified by a professional engineer who can visit the site to ensure that potentially important information has not been overlooked or omitted.
Based on your supplied information, I have assumed that no roof loading will be carried by this beam, just 2nd floor load and minimum attic load.
I can give you a couple engineered wood options for your 21’ span beam:
Triple 1-1/2” x 18” Versa-Lam 2.0 3100 DF
Quadruple 1-1/2” x 16” Versa-Lam 2.0 2800 DF
These are Boise Cascade products and you can go to the following link to find distributors in your area.
You will need to have a local engineer detail your connections, determine foundation requirements, and check your structure’s lateral stability due to the fact that you are removing a large portion of wall.
If you feel you have received a satisfactory answer to your question, click the Rating button that is appropriate. Experts are credited for each adequately Rated answer they provide. If you have additional questions, please let me know. Thanks