Yes, second layer. Warm weather crops like tomatoes, bell pepper, beans?, not much colder than sixty degrees. Cool weather crops like onions, cabbage, broccoli, etc., down to 40 or lower would be o.k. If I were you, for this year would consider starting cool weather plants in the greenhouse, and heat it in a minimal way. Get a light arrangement as described in threads on this site, and start your heat loving plants inside the house. Use a heat mat and have the room over 60 degrees.
Eclectic gardening style, drawing from 45 years of interest and experience. Mostly plant in raised beds and containers primarily using intensive gardening techniques.