Only factoring in the manufacturing cost (that is, not including the cost to haul to site and use) wood products are solidly carbon positive [1]. Lumber harvesting, hauling and processing is surprisingly efficient: It's a cutthroat business with razor thin margins.
The more important aspect is that something else would have been used instead. Each building that is of wood construction is one that wasn't built primarily with steel or concrete.
Also, effects of scale can be significant. As a simple example, there is about 200 billion kg of carbon sequestered in the contiguous US just in wooden telephone poles. If you can find a widescale use that makes economic sense, you make more immediate sinks. If you can also find ways of long-term sequestering the waste as it enters end of life, you can make ongoing gains in the CO2 balance.
The more important aspect is that something else would have been used instead. Each building that is of wood construction is one that wasn't built primarily with steel or concrete.
Also, effects of scale can be significant. As a simple example, there is about 200 billion kg of carbon sequestered in the contiguous US just in wooden telephone poles. If you can find a widescale use that makes economic sense, you make more immediate sinks. If you can also find ways of long-term sequestering the waste as it enters end of life, you can make ongoing gains in the CO2 balance.
[1] - http://articles.extension.org/sites/default/files/CIWP%20pub...