Measures being thought of embody voluntary targets for banks to enhance the typical energy performance certificate score of the properties of their lending portfolio to no less than band C by 2030.

These targets might grow to be necessary “if inadequate progress” had been made, in accordance with the paperwork.

It comes as ministers weigh choices after the conclusion of a session into the matter this yr.

Particulars of the inexperienced mortgage scheme, which might be one of the vital radical adjustments within the lending market for the reason that 2008 monetary disaster, come because the UK authorities introduced a stream of net-zero insurance policies forward of the Cop26 local weather summit in Glasgow this month.

Some lenders, resembling NatWest, have already launched inexperienced mortgage merchandise, providing a reduced rate of interest on properties with an vitality effectivity score of A or B. Halifax additionally gives a £250 cash-back incentive to clients shopping for probably the most vitality environment friendly properties.

Nevertheless, there are considerations that discouraging banks from having much less vitality environment friendly properties on their mortgage books would threat disadvantaging poorer clients, who might wrestle to enhance their property’s score.

The danger of not assembly mortgage necessities, or being refused a house mortgage, might power home consumers to spend hundreds of kilos on bettering their vitality effectivity.

It might additionally trigger a big rise in “mortgage prisoners” – folks trapped in contracts and unable to safe money-saving offers from new lenders refusing to tackle properties that are accountable for greater carbon emissions.

Sarah Coles, a private finance analyst at Hargreaves Lansdown, mentioned: “The issue is that whereas some properties might be improved at comparatively little value, different householders will discover it prohibitively costly.

“They could not have the ability to afford to borrow extra, or the price of adjustments to older properties could also be disproportionately excessive, so that they’d by no means recoup the price of the enhancements by a sale.”

House owners of listed properties might face additional monetary pressure, because it may very well be troublesome to make important adjustments to traditionally protected buildings.

The typical value of vitality effectivity enhancements for a single house is about £8,100, in accordance with a research by Nationwide Constructing Society. Nevertheless, that quantity rises to £25,800 for properties with a F or G vitality effectivity score.

The typical annual financial savings of “greening” a house are estimated at about £1,780 a yr, that means house owners of older properties would solely begin to reap monetary advantages after 14 years.

“Greening our housing inventory is significant if we’re to fulfill our local weather change obligations, and banks and finance suppliers are dedicated to serving to obtain this objective and ensuring customers are usually not left behind,” mentioned a spokesman for the banking foyer group UK Finance.

Particulars of the plan come after the federal government canvassed the finance business over the potential adjustments this yr. The transfer can be a part of a drive to improve as many properties as doable to band C scores by 2035.

“We’re working with mortgage lenders to assist householders to enhance the vitality efficiency of their properties and can publish our response to our lenders session in the end,” the federal government mentioned in its net-zero technique revealed on Tuesday.

A authorities spokesperson mentioned the vitality effectivity plans “is not going to impede folks’s means to get a mortgage”.

They added: “Now we have been partaking extensively with all kinds of stakeholders, together with lenders and shopper our bodies, to make sure that these with lower-performing properties have engaging and inexpensive choices for making inexperienced residence enhancements.”