Mr Spencer said the housing market is "performing better than we could have hoped for and the momentum looks set to build".
Item expects house prices to rise 2.3% in 2013 and 5.5% in 2014.
Various surveys have also pointed to rising consumer spending and recovering high street sales. Like-for-like retail sales rose 1.4% in June on a year earlier, following a 1.8% gain seen in May, an industry survey said recently.
Despite only modest increases in real incomes, Item expects consumer spending to increase 1.6% this year and 1.9% next year. However, it predicts the savings ratio will dip to 5.6% from 6.3% last year.
Total pay increased by 1.3% in the year to April, official figures showed recently, failing to keep pace with inflation of 2.7%.
The economy is widely expected to have grown by at least 0.5% in the second quarter, from 0.3% in the first quarter.
Item believes gross domestic product (GDP) will accelerate to 2.2% in 2014 and 2.6% in 2015.
Prof Spencer said: "There are hopeful signs for the world economy, which will lead to a pick-up in demand from the UK's key export markets.
"The US has successfully negotiated the fiscal cliff, the Chinese economy is beginning to rebalance away from investment to consumption, and there is also a move towards pro-growth policies in the eurozone.
"If managed successfully these factors could be a real boom for UK exporters."
It predicts export growth will remain subdued at 1.2% this year, before surging to 4.6% next year.
Item stands for Independent Treasury Economic Model, and uses the Treasury model for its analysis.