Critics question whether the interest rate will be low enough to attract sufficient up-take.
Others wonder how sufficient repayment can occur to the lenders from electricity bill savings and how they can reliably be claimed back over 25 years.
And there are questions about whether the work that could be carried out on properties will be of good enough quality to be effective, and save a sufficient amount of carbon emissions to help homes contribute their share of the 80% reductions required on all the U.K.'s emissions by 2050.
It doesn't matter. The Energy Act also requires energy companies to help fuel poor consumers under the Energy Company Obligation (ECO).
This will particularly target hard-to-heat homes and solid walled properties, and make them install smart meters, which will save you money, and make information on energy bills easier to understand.
Who will deliver it?
The Green Deal will be attractive to large organisations, but the processes for subcontracting specialist installation services, in compliance with the code of conduct, needs to be developed.
A number of local authorities are gearing up to deliver Green Deal schemes themselves, including Birmingham City Council and a cluster in the North East led by Newcastle City Council.
Councils are trusted and in a prime position to accept this responsibility.
They would also be in a good position to recover the loan repayments, as they already have a property-based system in place for council tax collection.
How much will be available?
The amount of the loans offered to households is expected to be up to £10,000.
Where will the money come from?
Financing could come via Government bonds, the Energy Saving Trust, the Ecofin Foundation, Marksman Consulting, the Climate Bonds Initiative, and tapping into utilities' ECO funds.
A Green Deal Finance Company is also to be launched this year, with big names signed up to it like British Gas, Carillion, Clifford Chance, E.ON, EDF Energy, Goldman Sachs, HSBC, Insta Group, Kingfisher, Linklaters, Lloyds Bank Corporate Markets, Mark Group, npower, PwC, RBC Capital Markets and Scottish and Southern Energy.
Who will do the work?
Service delivery could be dealt with by local firms, or contractors from larger organisations, providing much needed employment and training opportunities.
Where can I buy sustainable building products cheaply?
These are my favourite suppliers:
I have been disappointed by the paucity of information on their products given by the supposedly most 'green' of mainstream DIY stores: B & Q.
Are there any pilot schemes?
Yes. Pilot schemes are taking place, such as Gentoo’s Energy Saver Bundle pilot scheme in Sunderland.
BSI has a consultation underway on British Standard PAS 2030 – Improving the energy efficiency of existing buildings – a specification for installation process, process management and service provision.
And a consultation on training was conducted last year.
Will the finance be sufficient?
Wrapping homes in external insulation and replacing windows costs considerably more than £10,000 per house.
The best way to do the job effectively is to have a definite target for the airtightness and insulation value of the whole house, and to implement all the measures required at once.
This is because most homes are only renovated once every 30 years on average. Therefore not to do as much as possible while the builders are in, is a wasted opportunity and a wasted cost.
It is ideally necessary to spend between £30,000 and £50,000 per property, or one fifth the value of the property, if the total emissions and energy savings to be generated will be enough to meet the UK's carbon reduction targets. This is according to research done so far by pilot projects funded through the Technology Strategy Board as part of The National Refurbishment Centre and the Retrofit for the Future programme.
How will the assesment work?
The Government has issued a list of Qualifying Improvements, measures that will qualify for support.
The estimated savings from these measures and improvements have been included within new versions of the software used by assessors, RDSAP for dwellings, and SBEM and other compliance tools for non-domestic buildings.
The software will model the building, and some lifestyle factors, and rank the best options. It is likely that more than one option will be suggested in each case.
The building owner can then use this to get quotations from contractors for the works.
However, there is a fundamental shortage of hard data on the as-installed performance of many qualifying measures; and the complexity of multiple measures and their interactions are also not well understood.
There are doubts about whether installations will be up to standard and how this will be checked against expected performance.
Improving very poorly insulated or serviced buildings may have the result that occupants could accept a gain in personal comfort as opposed to savings on energy bills under the ECO; but how will this be financed?
A major issue is that the mechanisms for including wider scheme measures don't yet exist.
What if I can't do everything at once?
Then the optimum strategy is to have a long term plan for the property and not make earlier modifications that will preclude what will be done later.
Critics are pessimistic that the required level of savings will be reached, but new modelling by The European Alliance for Companies for Energy Efficiency in Buildings - EuroACE, a consortium of insulation and similar firms, has discovered that doing refurbishment in two stages rather than all at once could actually be more cost-effective.
The advantage of this approach is that the quick and cost-effective wins are tackled now, with a consequent immediate reduction in energy bills.
Then, later, perhaps between 2030 and 2035, buildings would receive a second pass which would allow them to achieve the 80% emissions reduction target.
By this time, it is anticipated that our experience and learning will have made it easier and cheaper to achieve the remaining gains.
Renovate Europe, a group campaigning for 3% of Europe's buildings to be renovated every year, is backing this approach.