Greetings. We have a bi-level built in 1972 that is currently sided with cedar. Underneath is the old 'black tarpaper' stuff--I don't know the correct name, DH does but he's not here ;). We have decided to go with vinyl siding and have gotten several estimates.
There is now a debate brewing regarding the use of Tyvek. Alhtough the cedar won't hold paint well (long story, something a prior owner put on the surface), the wood is still sound, not warped or rotted, so we can side right over it.) All contractors agree that we need 1/2" insulation to both level out the surface where the cedar laps between the 1st and second floors, as well as provide insulation. Most have recommended NOT using Tyvek in addition to the 1/2" : they feel due to our home's age it would become too airtight and cause problems. My husband is in agreement with this line of thinking- he wants the 1/2" insulation and nothing more. (His brother's newer home is too airtight, and as a result the family all suffers from higher than average respiratory illnesses in winter. ) Also, one contractor gave us an example of a customer who insisted on Tyvek over 1/2" insulation (although the contractor had tried to talk him out of it). The customer's house was so airtight when he opened the front door it caused a 'suction' effect thereby pulling on the back door.
The estimator who came by last night is really pushing the Tyvek over top 1/2" insulation (actually a newer product that Dow has out similar to Tyvek). He said he has never heard of the 'too much of a good thing' issue. He kept saying it will allow any moisture to get out, but none to get in, increase the R-factor, etc., etc.
My husband still does not want the Tyvek, but thought we'd post here and hopefully get some feedback/experiences on this issue.