The US Fed was a very large buyer of Mortgage Backed Securities, lower the rate of US mortgages. This means that they directly contribute to the housing rate increase. (This is in addition to the indirect aspect of lower long term rates raising equity prices, and people putting that money into houses)

https://www.newyorkfed.org/markets/mbs_faq.html

http://www.bloomberg.com/news/articles/2013-10-28/fed-sees-a...

http://www.marketwatch.com/story/fed-bought-up-half-of-agenc...