Local Law 97 & What It Means for Sustainability in NYC

Cities across the US have introduced carbon emissions legislation to do their part to combat climate change. The Big Apple leads the way with the biggest climate change legislation, the Climate Mobilization Act. Local Law 97 is one law within the Climate Mobilization Act that addresses carbon emissions of buildings in NYC to make them more sustainable.

We will discuss Local Law 97 (LL 97), what it means for building owners and managers, affordable housing, and how best to comply with the new directives.

NYC skyline on a sunny day. NYC Local Law 97 will help to make the largest buildings sustainable.

What is Local Law 97

Local Law 97 is a law under the 2019 Climate Mobilization Act that targets carbon emissions from the biggest buildings in New York City. Under Local Law 97, most buildings 25,000 square feet and larger will be required to meet carbon emissions cap, or implement energy efficiency standards, by 2024 in order to avoid significant fines. The carbon emissions cap will continue to tighten periodically. By 2030, most buildings 25,000 sq. ft. and larger will have to reduce their emissions by 40%. By 2050, NYC building emissions will need to be lowered by 80%. Individual buildings’ emissions from 2005 will act as the baseline from which emissions will have to be reduced.

Buildings are the leading contributor to greenhouse gasses and global warming in major cities. By capping carbon emissions from the largest buildings in cities across the world, legislators aim to slow the rate of global warming and reduce estimates of expected temperature increases in the coming decades to avoid worsening natural catastrophes.

Beginning in May of 2025, building owners and managers will have to submit annual emissions reports to prove that their NYC buildings are meeting the new sustainability standards set forth under Local Law 97.

What Does LL 97 Mean for New York City Building Owners

Buildings smaller than 25,000 square feet are exempt from Local Law 97. If you are the owner of a building 25,000 square feet or larger, see below to understand if you are affected by Local Law 97, and if that means you must adhere to carbon emissions caps for your building(s), or if you may opt for energy efficiency measures.

Flow Chart to determine if your building is affected by LL 97 and NYC carbon emissions cap.

If you are the owner of a building in New York City and you must adhere to carbon emission caps for your building to make it more sustainable, then you are subject to fines for failing to do so. Cases of intentionally misreported emissions on the annual Greenhouse Gas Emissions report can be punishable by fine and imprisonment.

To see the amount in fines you would face for your building if you failed to meet the carbon emissions cap, use this NYC LL97 Carbon Emissions Calculator.

Highrises in NYC. Affordable housing can retrofit windows among other energy efficiency measures.

Affordable Housing and Local Law 97

Under Local Law 97, certain buildings that meet the 25,000 square footage threshold to trigger NYC carbon emissions cap requirements have alternatives to meeting the 40% carbon emissions reduction. Local Law 97 Guidance for Affordable Housing outlines which buildings have options available to them. This includes buildings that have at least 35% of its units rent-regulated, among others.

These buildings have the option to prove by December 31, 2024, that they have taken steps to improve their buildings energy efficiency. The Prescriptive Energy Conservation Measures include installing individual temperature controls and air sealing windows.

The combined benefit of all of the listed energy conservation measures will drastically improve the sustainability of large NYC buildings that would otherwise be unduly burdened by carbon emissions caps. Insulating windows, walls, and ceilings and giving residents of these buildings temperature control abilities will go a long way to improving their safety and quality of life.

Thermostat. Under LL 97, buildings will be safer & more sustainable with energy efficiency measures.

Retrofit Windows vs. Replacement Windows

Windows account for 20% of a building’s energy loss. A window upgrade project will go a long way in making your building more energy efficient and compliant with increasingly popular carbon emissions cap legislation, such as Local Law 97.

For window upgrade projects, your options are to retrofit your windows or replace them. Replacing windows means removing every part of the window, frame and all. This is the most invasive, expensive, time-consuming option, and it requires hiring professionals.

When talking about retrofit windows, there are two main options: replacing the window sash or fitting the frames with window inserts. Replacing the sash means the frame stays in place while the moving panels (single, or double-hung) are removed. Replacing the sash is an invasive process, but far less so than window replacement. The parts are more affordable, and a savvy DIYer can complete the project on their own. However, seeking professional assistance is recommended since improper replacement of a window sash can have the opposite effect than the intended energy efficiency upgrade.

Window Replacement Window Retrofit
Type (Entire Frame Replaced) Sash Replacement Window Inserts
Time 1-6 Hours ~3 Hours 15-Minute Installation
Cost $$$ $$ $
Difficulty Professional Required Professional Recommended DIY

Window inserts as a window retrofit project are the most affordable and least invasive option for energy efficiency upgrades. And with Local Law 97 addressing NYC’s largest buildings, the cost, time, and level of invasiveness of energy efficiency upgrades are important factors to take into account. This least invasive retrofit project, as opposed to frame or sash replacement, will allow you to avoid pausing work and life schedules to complete.

Man installing Indow window inserts in NYC. Retrofitting windows makes buildings more sustainable.

Indow & The Clean Fight New York

The Clean Fight New York is a not-for-profit accelerator program in its second year. It was created to identify CleanTech companies and assist them in scaling their products for use in NYC to make buildings more sustainable, in a way similar to that prescribed in Local Law 97. The Clean Fight selects three start-ups each year for each designated area of building energy efficiency. This year the categories are Smart Electrification, Advanced Optimization, and Envelope Efficiency. Indow was the only start-up included in the Envelope Efficiency category addressing energy loss through windows.

4,850 garbage trucks would be needed to haul the 72,0750 tons of carbon Indow inserts have blocked.

With buildings 25,000 square feet and larger requiring drastic measures to reduce carbon emissions and energy usage in compliance with Local Law 97, full window frame or sash replacement is not financially feasible for building owners and managers. The Clean Fight New York is connecting building owners and managers with CleanTech companies, and providing the blueprint for others as they begin the daunting task of making their huge buildings more energy efficient.

Read about the Department of Energy’s study of Indow inserts to learn more about why our inserts were chosen for The Clean Fight New York and how they can help your NYC building become sustainable and meet energy conservation measures under Local Law 97.

Customer Reviews


4.49 Average 1477 Reviews logo

Matthew L

Indow inserts were easy to measure, order and install. They've provided great insulation for old single-pane and stained glass windows in an antique home. We can significantly feel how much better the home holds heat.

Posted 2 days ago

Ellis W

I ordered two Indow inserts for my home. They are doing a great job, entirely happy with them and the ordering process.

Posted 1 week ago

Elizabeth W

I can't say enough good things about this product and company. Our house is 101 years old and the sidelites next to our front door are single pane ancient wavy glass which means when it gets very cold (Chicago temps) we can have an inch of frost covering the INSIDE of our windows. I was desperately searching for a solution so our front vestibule was not so cold and a friend recommended Indow. The process could not have been simpler and the temperature difference it has made is off the charts.

Posted 2 weeks ago

Austin T

I have several historic single pane gridwork mullion windows. They're beautiful but have almost no thermal protection. Indows proved to be the perfect solution to preserve these windows while getting the thermal comfort we need. They were easy to install and work perfectly!

Posted 3 weeks ago

Kathryn M

Amazingly easy to install even the safety chain holders. I. Noticed an immediate sound level difference and the room atmosphere became more solid feeling and pleasant. They also gave an insulating feature to the window drafts are non existent! The house is 50ft off a State highway that is heavily traveled in warmer months I'm confident the indows will handle it. I'm very pleased!

Posted 1 month ago


We ordered the acoustic inserts to help with road noise, and we've been sleeping so much better with them!

Posted 1 month ago

Sienna K

We used the windows inserts in our skylight. They are great! They the horrible drafts and noise out and were cost efficient. My only comment would be to provide better measurement and installation instructions for skylights specifically. It took us a lot of guessing and research to measure and install because skylight directions were not provided and the windows install guide doesn't always apply to skylights. Other than that though great product and I would buy again!

Posted 1 month ago

ted t

Our home was built in the late 1800s and we have spent a lot of money over the last 20+years restoring it.We did not want to replace the windows with modern windows because of the cost and originality. But the single pane windows come with a price also. the main reason we purchased the Indow window inserts is because of the condensation on the inside of the windows.We would literally have a take a towel and wipe them down every morning in the winter. There would be a puddle on the sill,and wood and water dont get along to well. SO we looked into the best solution to our problem and found Indow. Was reluctant to spend that much money but am super glad we did!! They have been installed now for over two months and our condensation problem has been virtually eliminated.!!! AND our furnace does not run as much as it did before. Over all it was money well spent!! The process was a little scary at first but they have a simple formula. And our contact person,Reed was awesome. Answered any questions i had and was always available.

Posted 1 month ago


Used to block interior side of a garden window in the the kitchen. Without insert, cold air literally poured into the kitchen making a winter jacket almost mandatory when preparing meals or washing dishes

Posted 1 month ago

Rob S

Highly recommend! The team (Brian) took time to help me figure out the best solution. They were made and delivered faster than expected. It was very rewarding to install them because I could feel the cold air get squeezed out as they went flush against the single pane of glass. Solid quality and great fit.

Posted 1 month ago

Alexa L

My inserts fit beautifully into my 125 year old windows - many of which were 5 feet tall. Easy to unwrap and install. Great product and even better service! I liked the process of measuring the windows with a laser measuring tool which was easy to use and precise. The product came in good condition after shipping across country and was well marked. The customer support was excellent.

Posted 1 month ago

Sarah D

Received our Indow Windows and can tell they are blocking a lot of the noise we could hear. Right now the weather is mild, but hoping to notice a big difference when the summer heats up. Our house is in a historic district and we cannot change our windows. They are very drafty and thin glass. We only ordered two, but we are in the process of ordering for four more. Love that we don’t need to drill holes or anything and they just pop right in.

Posted 1 month ago

Allan F

Every thing arrived in perfect condition, thanks to the very secure packaging. Windows fit as expected, although quite tight. After installation we noticed that the cold drafts were gone and the room felt a lot warmer. We are very satisfied with the product and the result.

Posted 1 month ago

Adriana W

Great customer service! Super satisfied with our windows.

Posted 1 month ago

Thomas M

Indow service and product is good. Reduced outside noise considerably.

Posted 2 months ago