Everwarm becomes the fourth business to join the Lakehouse group since 2011.

The merger will see Everwarm’s 250 staff become part of Lakehouse which will now employ 1,200 staff.

Everwarm has installed carbon-saving measures in more than 45,000 homes and businesses across the UK from its offices in Bathgate in West Lothian and Bedford in the east of England.

In the last financial year – only its third year of trading – Everwarm recorded a turnover of £46m and pre-tax profits of £6m.

Lakehouse had a turnover of £190m in 2012/13 making a pre-tax profit of £7.1 m

Everwarm joins the group through an all share deal, with the merger taking place debt free and maintaining Lakehouse’s low gearing levels.

Michael McMahon, managing director of Everwarm, said: “Our deal with Lakehouse is the result of a year-long search for a suitable partner.

“Rather than a corporate investor, we were looking to join with a business that would allow us to diversify our range of services and help us build on our success to date.

“Now, we look forward to growing our English operation within the Lakehouse group and bringing a wider asset management offer to clients in Scotland.”

Stuart Black, executive chairman of Lakehouse, said: “This merger represents another milestone in Lakehouse’s programme of acquiring successful, complementary businesses that expand our capabilities and reach.

“With so much debate about the direction of policy in the sustainability sector, we see this deal as a vote of confidence in the green economy and the fact that energy efficiency, fuel poverty and zero carbon homes are going to remain central to any government’s agenda.

“Sustainability is a fundamental plank of our business and we’ll be drawing on Everwarm’s impressive delivery record in Scotland to expand our retrofit division.

“There are huge opportunities in London and south east England – a domestic market which is remarkably immature in terms of retrofit and energy efficiency.”

The addition of Everwarm to the Lakehouse group follows three recent acquisitions: K&T Heating Services, a gas servicing, installation and compliance business, in 2011; Allied Protection, a West Sussex-based fire safety and compliance specialist, in 2012; and East-Anglia based Foster Property Maintenance, a contractor and property services company working in the affordable housing and public property sectors, in October 2013.