A key factor is whether the old paint has been removed down to bare wood. In cases where old paint remains, continue with the oil-based system you have been using. (Things to keep in mind to maximize job life:
- spread rate should be kept in the range recommended by the manufacturer; spreading primer or paint too thin will compromise stain blocking, mildew resistance, and crack resistance;
- joints and caulking should be done properly to keep moisture out, or let it run out, as appropriate; I suggest using a top quality acrylic latex clear caulk, as recommended by your paint supplier; allow caulking to dry at least one day before applying a coating over it.)
In cases where the paint is stripped to bare wood, use a top quality acrylic latex system:
- be sure to apply primer within a few days;
- use a top quality latex exterior wood primer; your current primer supplier can recommend one; be sure to apply an adequately heavy coat of the primer;
- for the finish coat, go with a top of the line exterior acrylic latex flat, satin, semigloss or gloss paint; your current finish coat supplier can recommend these;
- with water-based primers and paints, it is essential that application and curing be at appropriate temperatures: application at too low a temperature can compromise film formation. This means the paint should not be applied when the air temperature is below the stated figure for the product, nor if the temperature is forecasted to drop below that minimum during the next 36 hours. Also, the surface being painted should not be below that temperature. What can happen is that the lower temperature makes the particles of binder get so hard that they won't fuse sufficiently into a tough, continuous film If this happens, while the paint may look fine, it may crack or peel or otherwise loose adhesion in a relatively short time, say a year or two rather than say in 15 years.
In extreme cases, the paint will be cracked and/or easily chipped off after it has dried. Color can be affected in that they paint may dry to a lighter color than it is supposed to. Low temperature application can also lead to surfactant leaching, which is described in the problem solver section of our web site. And application of water-based coatings under conditions that lead to too fast a dry can also compromise film formation and thus reduce durability. Thus, avoid priming or painting in direct sunshine and when it is dry and breezy or is very hot (over 95 degrees F).